WoW Classic: what items are useful for me and which are vendor trash?

Usefulness of various common-quality looted items

Bear Meat: Two recipes: Blood Sausage (60-100-120-140, recipe bought from Old Town in Stormwind) and Smoked Bear Meat (40-80-100-120, recipe bought from Loch Modan (Thelsamar) or Silverpine Forest (The Sepulcher))
Big Bear Meat: Cooked into Big Bear Steak (110-150-170-190).
Boar Intestines: Used only in the essentially Alliance-only recipe Blood Sausage, 60-100-120-140. Sells for 18c.
Boar Ribs: Two recipes: Dry Pork Ribs (80-120-140-160, requires one + Mild Spices) and Succulent Pork Ribs (110-130-150-170, requires two + Hot Spices)
Buzzard Wing: Barbecued Buzzard Wing learnable at 175 and turns grey at 255 (recipe)
Clam Meat: Used for Boiled Clams 50-90-110-130 and Clam Chowder 90-130-150-170
Chunk of Boar Meat: Cooked into Roasted Boar Meat, 45-65-85, recipe learned from trainers.
Core of Earth: reagent in BS and LW recipes, skill level 260-ish, creates items of item level 50. Sells to vendors for 4s.
Core of Elements: only used in two quests, one repeatable; 30 of them are turned in at Light's Hope Chapel for one Insignia of the Dawn. Sells to vendors for 2s. Basically trash after TBC releases.
Coal: reagent only for Smelt Steel, sold by Trade Goods vendors for around 5s, sells to vendors for 1s 25c, don't even bother to AH it.
Coarse Gorilla Hair: used in one Leatherworking recipe, skill level 200, hard to sell, nobody cares after TBC came out. Sells to vendors for 6s 8c.
Crisp Spider Meat: Cooked into Redridge Goulash, 100-135-155-175, basically Alliance-only recipe, sold in Stormwind and as a quest reward. Sells for 50c.
Crunchy Spider Leg: A low-level drop added in TBC, can be cooked into Crunchy Spider Surprise, 60-100-120-140, recipe only sold in Ghostlands and Bloodmyst Isle. Sells for 12c.
Dampscale Basilisk Eye: only used to grind back Scryer reputation if one went with Aldor and want to switch. Barely worth auctioning. Sells for 6s 76c.
Deeprock Salt: used in one LW recipe (to create Cured Thick Hide, used in 17 other recipes, so quite wanted), one Cooking recipe and one Engineering recipe. AHs for >17s on the server I'm on. Sells to vendors for 2s 50c.
Dreadfang Venom Sac: Dropped in Terokkar Forest, used to switch factions from Scryers to Aldor.
Elemental Earth: used in a bunch of crafting recipes around skill level 200, creating item level 40-ish items. Sells to vendors for 4s.
Enchanted Water: has a few uses, but either AH it or just vendor it. Sells for 1s 33c.
Essence of Fire: lots of stuff, Classic end-game recipes and the like.
Fertile Spores: Turned in six at a time for Sporeggar reputation.
Fish Oil: Used only as a reagent for water walking by Shamans. Sells for 7c.
Flask of Big Mojo: some use in three LW and JC recipes between 240–300. Sells to vendors for 5s. Probably not worth trying to AH.
Flask of Mojo: some use in LW, JC, Engineering, in recipes between 210–260ish. Sells to vendors for 2s 50c.
Ghost Mushroom: used in five high-level (250ish) Alchemy recipes.
Giant Egg: the quest Clamlette Surprise (which needs 12), Cooking (1 recipe, Monster Omelet, 225-250-262-275, 1 egg and 2 Soothing Spices per cast)
Gooey Spider Leg: Cooked into Gooey Spider Cake, 100-150-170-190, recipe only sold in Stormwind.
Goretusk Liver: One recipe: Goretusk Liver Pie, 50-90-110-130. Objective of the Westfall quest of the same name, which needs 8 of them. The quest awards the recipe, but it can also be bought from Stormwind's Old Town. Low drop rate. Sells for 15c.
Goretusk Snout: Reagent for Westfall Stew, 75-115-135-155. Sells for 27c.
Gorilla Fang: Objective of the quest Stranglethorn Fever, which needs 10. Not used in any crafting recipe, no other use. Sells for 67c.
Great Goretusk Snout: Only used for the quest Redridge Goulash, which requires five. No other uses. Sells for 50s.
Heart of the Wild: Tailoring (225, for blue items), Engineering, Alchemy, JC
Huge Venom Sac: only used for TBC antivenom by Rogues, sells for 15s.
Jaggal Clam Meat: Cooking, one recipe (Clam Bar), 300-320-330-340. Sells for 7s.
Large Fang: Used in two Leatherworking recipes (one blue, one green, skill ~150), three Blacksmithing recipes (all green, skill ~180), one Enchanting recipe (skill 175), and one Alchemy recipe (Great Rage Potion, skill 175). AH'able, but hard to sell.
Large Venom Sac: AH'able. Sells for 1s 85. Used in one Alchemy recipe (Elixir of Poison Resistance, 120-185), Rogues' Instant Toxin spell, and First Aid's Strong Anti-Venom (130-200).
Lean Wolf Flank: Two recipes: Lean Wolf Steak (125-165-185-205, recipe bought from the traveling Super-Seller 680 in Desolace), and Seasoned Wolf Kabob (100-140-160-180, recipe bought from Stormwind, or rewarded from an Alliance quest in Duskwood). More trouble than it's worth if you're Horde.
Lion Meat: Cooked into Hot Lion Chops (125-175-195-215, 1 + Hot Spices) and Tasty Lion Steak (150-190-210-230, 2 + Soothing Spices)
Living Essence: Used in many late-vanilla crafting recipes: Leatherworking 270, Enchanting 300, Engineering 265, Tailoring 290, Alchemy 270 (one Transmute recipe)
Long Elegant Feather: used only in one Tailoring recipe (Admiral's Hat, which requires six feathers; skill 240–285), and in one Horde quest (Another Message For The Wildhammer). Sells for 5s 30c.
Long Tail Feather: used in one Leatherworking recipe, to create supposedly OP hunter gloves, but barely sells in the AH. Sells to vendors for 3s 3c.
Murloc Eye: The only use is in making Westfall Stew, 75-115-135-155; the recipe is only sold in Stormwind or obtained from an Alliance quest. Sells for 16c.
Murloc Fin: Two of them are cooked into Murloc Fin Soup (90-130-150-170); objective of Murloc Poachers (Redridge Mountains, requires eight)
Mystery Meat: Cooking, three recipes, two of them (Carrion Surprise, Mystery Stew) 175-215-235-255, the third (Dragonbreath Chili) is 200-225-237-250.
Nightmare Vine: Used for TBC Alchemy, skill level 350-ish onwards. Sells for 12s 50c.
Raptor Egg: Cooked into Curiously Tasty Omelette, 130-170-190-210, recipe sold in Stormwind (Alliance-only) and Arathi Highlands and Stranglethorn Vale (both Horde-only trade goods vendors).
Raptor Flesh: Cooking, Roast Raptor, 175-215-235-255, recipe bought from Desolace (from the traveling Vendor-tron 1000), Arathi Highlands, Dustwallow Marsh and Stranglethorn Vale (faction-specific vendors in all these zones).
Raptor Hide: Used for 3 leatherworking recipes but not worth AHing for like 2s 30c when it vendors for 2s 8c.
Raw Spinefin Halibut: There is no cooking recipe, it's just vendor trash. Sells for 1s 60c.
Raptor Ribs: one Cooking recipe, 335-355-365-375
Red Wolf Meat: Cooking, Hot Wolf Ribs, 175-215-235-255, recipe bought from Super-Seller 680 in Desolace, or faction-specific vendors in Feralas.
Sandworm Meat: the only meat that can be cooked up to skill level 300, one recipe (Smoked Desert Dumplings), 285-310-322-335, recipe learned from a quest that requires Cooking 285 to pick up from Calandrath, the innkeeper at Cenarion Hold in Silithus. (Take this quest while you farm.)
Savage Frond: turn in 30 at a time for Argent Dawn reputation and an Insignia of the Dawn. Sells for 2s. Basically vendor trash.
Shadow Silk: A lot of Tailoring recipes for green items, and two Engineering items. Sells for 10s.
Sharp Claw: Used for two Blacksmithing recipes (green items, skill levels 160 and 175) and one Alchemy recipe (Rage Potion, skill level 60-130). Sells for 45c.
Shiny Fish Scales: used only for Shamans' Water Breathing, marginal AH, Sells for 7c.
Slimy Murloc Scale: Used in two low-level green Leatherworking recipes (around skill level 90). Sells for 75c.
Small Egg: Sells for 4c. Used for low-level cooking (Herb-Baked Egg, learned from trainers, 1-45-65-85. Also used during the Feast of Winter Veil, to make Gingerbread Cookies and Egg Nog, very sought after at this time.
Small Spider Leg: Cooking, Kaldorei Spider Kabob, 10-50-70-90, recipe only obtained as an Alliance quest reward in Teldrassil. Sells for 3c.
Small Venom Sac: Only one use, for the First Aid recipe Anti-Venom, 80-80-115-150, learned from trainers. Sells for 82c. You can make a two copper profit by turning each Small Venom Sac into three Anti-Venom, which sell for 28c each.
Solid Stone: also a mining reward, mined from mithril nodes, used in Engineering and Blacksmithing in recipes between 175 and 200 skill level, used to create further reagents or recipe parts, no valuable items. Sometimes easy to sell on the AH, can sell for around 25s each. Sells to vendors for 1s.
Spider Ichor: Cooked into Blood Sausage, 60-100-120-140, recipe only sold in Stormwind
Spider's Silk: Tailoring, three green items and one blue item; one Leatherworking recipe for a blue item.
Strange Spores: Cooked into Sporeling Snack (310-330-340-350). Sells for 2s.
Stringy Vulture Meat: Only used for Westfall Stew, 75-115-135-155.
Tangy Clam Meat: Cooked into Goblin Deviled Clams, 125-165-185-205, learned from trainers. (Recipe also needs 1 Hot Spices.)
Tender Crab Meat: used only in one recipe, Spiced Chili Crab (225-250-262-275, also needs 2 Hot Spices, recipe sold in STV (Uthok at Grom'Gol) or Swamp of Sorrows (Banalash at Stonard) or Westfall (Kriggon Talsone at the very southwestern tip of the mainland))
Tender Crocolisk Meat: Cooked into Crokolisk Gumbo (120-160-180-200, needs one + Hot Spices, Alliance-only recipe) and Heavy Crokolisk Stew (150-160-180-200, needs two + Soothing Spices, Horde-only recipe)
Tender Wolf Meat: Cooking, one recipe, 225-250-262-275.
Thick Murloc Scale: Two Leatherworking recipes (a green chest 170-210 and green wrist armor 190-230). Sells for 5s.
Thick Spider's Silk: Four Tailoring recipes, one Gnomish Engineering one (Gnomish Net-o-Matic Projector), one Leatherworking recipe.
Vibrant Plume: used for a neutral Darkmoon Faire quest; turn in five Vibrant Plumes for 12 Darkmoon Faire Prize Tickets.
White Spider Meat: Cooking, 200-225-237-250 (only one recipe, Spider Sausage)
Wicked Claw: Used in two recipes: the purple Lionheart Helm, a level 300 blacksmithing recipe, which needs 40; and the blue Wolfshead Helm, a level 225 leatherworking recipe, which needs 8. AH'able, but hard to sell
Zesty Clam Meat: Cooking one recipe (Undermine Clam Chowder), 225-250-262-275. Also needed for the quest Clamlette Surprise (which needs 10), received in Gadgetzan from Dirge Quikcleave, which is the only way to learn Cooking up to level 300. Sells for 50s; the cooked version, Undermine Clam Chowder, sells for 1s, but requires two Clam Meats plus Hot Spices (~40c) and Ice Cold Milk (~1s), so cooking for vending is unprofitable.

All the different fish and the levels they're cooked at

Barbed Gill Trout: Outland fish, found in all Outland outdoor zones, Deadwind Pass, Serpentshrine Cavern, Underbog. Two recipes: Blackened Trout (300-320-330-340, recipe bought from Zangarmarsh) and Stewed Trout (335-335-345-355, recipe bought from barmaid Kylene in Shattrath).
Big-Mouth Clam: Contains Zesty Clam Meat
Bloodfin Catfish: Added in TBC, fished in Deadwind Pass. Cooked into Broiled Bloodfin, 300-320-330-340, the recipe is a green item and is contained in a cooking daily quest reward item.
Darkclaw Lobster: Only fished in Azshara, and according to comments requires a very high fishing level, close to 300. Can be made into Lobster Stew, 275-315-335-355, one of the few recipes that can be used to get to cooking level 300. The recipe can only be bought in Feralas.
Darkshore Grouper: Only fishable in Darkshore. Objective of an Alliance quest that awards a fishing pole. Not used for any recipe, but can be eaten and fed to pets.
Deviate Fish: Reagent for an Alchemy recipe (Elixir of Giant Growth, recipe is a rare drop from The Barrens, 90-120-140-160) and one Cooking recipe (Savory Deviate Delight, also a drop from the Barrens, 85-125-145-165)
Deviate Scale: Not a fish, but fished in the Barrens where Deviate Fish are also fished. Only used for Leatherworking recipes in the 90 to 150 range.
Figluster's Mudfish: Outland fish, fished in Nagrand and Netherstorm. Cooked into Grilled Mudfish, 320-340-350-360, recipe bought from faction-specific vendors in Nagrand.
Firefin Snapper: Only used for the Alchemy recipe (learned from trainers, 130-150-160-170) that creates Fire Oil.
Fish Oil: Also not a fish, but can be fished in Desolace. Used for the Shaman spell Water Walking, otherwise junk.
Furious Crawdad: Outland fish, only fished from a few mountain lakes in Terokkar Forest, accessible only by flying mount. Cooked into Spicy Crawdad, 350-370-380-390, recipe bought from faction-specific vendors in Terokkar Forest.
Golden Darter: Outland fish, fished in Zangarmarsh and Terokkar Forest. Cooked into Golden Fish Sticks, 325-345-355-365, recipe bought from faction-specific vendors in Terokkar Forest.
Icefin Bluefish: Outland fish, fished in Nagrand and Netherstorm. Cooked into Poached Bluefish, 320-340-350-360, recipe bought from faction-specific vendors in Nagrand.
Large Raw Mightfish: Also fished only in Azshara, reagent for Mightfish Steak, another one of the few recipes to get to 300 (275-315-335-355), recipe bought from Feralas.
Lightning Eel: Useless, only used in a turn-in quest in the Eastern Plaguelands (at Light's Hope Chapel), where 30 can be exchanged for an Insignia of either the Crusade or the Dawn.
Oil Covered Fish: Fished in Stonetalon Mountains, in Windshear Crag. No cooking recipe, a very weak food (61 health), sells for 1 copper, vendor trash.
Oily Blackmouth: Reagent for the Alchemy recipe for Blackmouth Oil (80-80-90-100), taught by trainers.
Raw Brilliant Smallfish: One of the first fish fished. Can be cooked into Brilliant Smallfish, 1-45-65-85. The recipe can be bought from Fishing Supplies vendors in Thunder Bluff, Undercity, Stormwind, Dun Morogh, Loch Modan, Mulgore, Elwynn Forest, Teldrassil (cooking supply vendor, Nyoma) and Tirisfal Glades.
Raw Bristle Whisker Catfish: A common low-level fish, fished in zones like Ashenvale, Stranglethorn, Stonetalon, The Barrens, and the capitals (but not Ironforge (except in TBC)). Cooked into Bristle Whisker Catfish, 100-140-160-180, and the recipe can be bought from Cooking and Fishing suppliers in Stormwind, Thunder Bluff, Undercity, Ratchet, and Hillsbrad (both Southshore and Tarren Mill).
Raw Glossy Mightfish: High-level fish. Cooked into (225-265-285-305) Cooked Glossy Mightfish, and the recipe can only be bought from Kelsey Yance, the cook in The Old Port Authority building in Stranglethorn Vale.
Raw Greater Sagefish: Both raw and cooked fish restore mana. Fished in Alterac and Stranglethorn. Cooking skills 175-215-235-255, recipe bought from Cooking Supplies vendors in the capital cities, Micha Yance in Southshore in Hillsbrad, Kelsey Yance in Booty Bay, and a few other places.
Raw Loch Frenzy: Created into Loch Frenzy Delight, 50-90-110-130, recipe bought from Khara Deepwater outside Thelsamar in Loch Modan. Alliance-only.
Raw Longjaw Mud Snapper: One of the most common fish, rivalling Raw Bristle Whisker Catfish. Cooked into Longjaw Mud Snapper, 50-90-110-130, recipe bought from Fishing Supplies vendors in surprisingly few places: Thunder Bluff, Ironforge, Loch Modan, Mulgore, Undercity, Elwynn, Silverpine, Teldrassil.
Raw Mithril Head Trout: Cooked into Mithril Head Trout, 175-215-235-255, recipe sold in Hillsbrad (Alliance only), Stranglethorn (Kelsey Yance), Ironforge, Undercity, Orgrimmar, Wetlands, couple of other places.
Raw Nightfin Snapper: Cooked into Nightfin Soup, 250-290-310-330, recipe bought from Gikkix at Steamwheedle Port in Tanaris.
Raw Rainbow Fin Albacore: Cooked into Rainbow Fin Albacore, 50-90-110-130, recipe bought from many places, fishermen and Fishing Supplies vendors in Stormwind, Orgrimmar, Barrens, Westfall, Wetlands, Teldrassil, Durotar, Undercity, Silverpine.
Raw Redgill: Cooked into Filet of Redgill, 225-265-285-305, recipe only available from Kelsey Yance in the Old Port Authority Building, Booty Bay, Stranglethorn Vale.
Raw Rockscale Cod: Cooked into Rockscale Cod, 175-190-210-230, recipe sold in Stranglethorn Vale (Kelsey Yance, Booty Bay), and fishing suppliers in Ironforge, Undercity, Orgrimmar, Darkshore, Hillsbrad (Southshore, Alliance only), a couple of other zones.
Raw Sagefish: Cooked into Smoked Sagefish, 80-120-140-160, recipe available from quite a few places: Cooking Suppliers in Thunder Bluff, Stormwind, Orgrimmar, Undercity, Ironforge, Darnassus, Shattrath, Silvermoon, Azuremyst Isle, Exodar, and others.
Raw Slitherskin Mackerel: One of the common low-level fish, very ubiquitous, also in drops from water-adjacent mobs. Cooked into Slitherskin Mackerel, 1-45-65-85, but the recipe is available from surprisingly few places, all Fishing Suppliers or Fishermen: Tansy Puddlefizz in Ironforge, Martine Tramblay outside and to the east of the road to Undercity in Tirisfal Glades, Kriggon Talsone at the very southern tip of the shore of Westfall, Zansoa at Sen'Jin Village in Durotar, and finally Nessa Shadowsong at Rut'theran Village in Teldrassil.
Raw Spinefin Halibut: Cannot be fished, only obtained as a drop. Cannot be cooked either: they forgot to put the recipe in. Their only use is as a mediocre food, 1392 health over 30 seconds. Sells for 1s 60c.
Raw Spotted Yellowtail: Cooked into Spotted Yellowtail, 225-265-285-305, recipe bought from Gikkix at Steamwheedle Port in Tanaris.
Raw Summer Bass: A high-level fish. Cooked into Hot Smoked Bass, 240-280-300-320, recipe bought from Kelsey Yance at Booty Bay, Stranglethorn Vale.
Raw Sunscale Salmon: Cooked into Poached Sunscale Salmon, 250-290-310-330, recipe bought from Gikkix at Steamwheedle Port in Tanaris.
Raw Whitescale Salmon: Cooked into Baked Salmon, 275-315-335-355, recipe bought from Feralas.
Sickly Looking Fish: Fished in the Undead zones of Undercity, Tirisfal Glade and Silverpine Forest. Not a reagent for anything, barely worth it as food (restores 30 health over 15 seconds), sells for 1 copper.
Spotted Feltail: Outland fish, fished in Zangarmarsh, Terokkar Forest, Serpentshrine Cavern, Underbog. Cooked into Feltail Delight, 300-320-330-340, recipe bought from Zangarmarsh.
Zangarian Sporefish: Cooked into Blackened Sporefish, 310-330-340-350, recipe bought from a vendor (Juno Dufrain) at Cenarion Refuge in Zangarmarsh.

Enchanting materials progression

Strange Dust < Soul Dust < Vision Dust < Dream Dust < Illusion Dust < Arcane Dust (TBC) < Infinite Dust (WotLK).

Strange Dust: First dust used, from Runed Copper Rod (1-10) and Chest Minor Health (15-70-90-110) (both needing 1) to Boots Minor Stamina (125-150-170-190, needing 8) and Chest Lesser Absorption (140-165-185-205, needing 2 + 1 Greater Astral Essence + 1 Large Glimmering Shard).
Lesser Magic Essence: Skills learned at 20, 40, 45, 60, 80 (plus 1-10 for Runed Copper Rod), going green at 100, 110, 115, 125, 135 and finally the last one going grey at 155.
Greater Magic Essence: Skills learned at 70, 80, 90, 100, going green at 130, 135, 140, 150 and going grey at 150, 155, 160, 170.
Small Glimmering Shard: Four recipes, learned at 90, 110, 115, 115, going green at 140, 150, 160, 160 and going grey at 160, 170, 180, 180.
Large Glimmering Shard: Four recipes, learned at 140, 140, 145, 150, going green at 185, 185, 190, 195 and going grey at 205, 205, 210, 215.
Lesser Astral Essence: Ten recipes, learned from 105 to 145, going green at 150 to 170, and going grey at 170 to 190.
Greater Astral Essence: Five recipes, learned from 135 to 150, going green at 180 to 195, and going grey at 200 to 215.
Soul Dust: 18 Enchanting recipes plus one Jewelcrafting recipe. Enchanting recipes learned from 130 to 170, going green at 175 to 210, and going grey at 195 to 230. (The recipes for Boots Lesser Stamina and Bracer Stamina are particularly valuable, needing only dust.)
Lesser Mystic Essence: 9 recipes, learned at 155–190, going green at 195–230, going grey at 215–250.
Greater Mystic Essence: 8 recipes, learned at 175–200, going green at 215–240, going grey at 235–260. Also needed for Runed Truesilver Rod.
Lesser Mystic Essence: 9 recipes, learned at 155–190, going green at 195–230, going grey at 215–250.
Small Glowing Shard: Three recipes, learned at 155 & 175, going green at 195 & 215, going grey at 215 & 235.
Large Glowing Shard: Five recipes, learned at 190–200, going green at 230–240, going grey at 250–260.
Vision Dust: Twenty recipes (21 in TBC, 22 in WotLK), learned at 175–225, going green at 215–265, going grey at 235–285. Boots Stamina and Chest Superior Health are a vital part of leveling enchanting, since they need only dust, which can be easily obtained from tailored Mageweave items.
Lesser Nether Essence: Nine recipes, learned at 205–230, going green at 245–270, going grey at 265–290.
Greater Nether Essence: Six recipes, learned at 230–245, going green at 270–285, going grey at 290–305.
Small Radiant Shard: Three recipes, learned at 225/230/265, going green at 265/270/305, going grey at 285/290/325.
Large Radiant Shard: Six recipes, learned at 235–250, going green at 275–290, going grey at 295–310. (Plus one Jewelcrafting recipe added in TBC.)
Dream Dust: 13 enchanting recipes, learned at 230–270, going green at 270–310, going grey at 290–330. Also used in 1 Alchemy recipe and 3 Tailoring recipes, and additionally 1 Mining recipe in WotLK. Boots Greater Stamina and Shield Greater Stamina are an excellent way to power through the last 40 levels of Classic Enchanting, using only dust.
Lesser Eternal Essence: 6 recipes (8 in WotLK), learned at 255–300, going green at 295–325, going grey at 315–340. Additionally there's Enchanted Leather, 250-250-255-260.
Greater Eternal Essence: 20 recipes (12 in WotLK), Classic endgame material, with some (deleted) recipes using 12 of these. Learned at 275–300, going green at 305–325, going grey at 320–340. Required for both Runed Arcanite Rod and Runed Fel Iron Rod. Additionally used by Tailors, two at a time, for Enchanted Runecloth Bag, 275-290-305-320.
Small Brilliant Shard: 5 recipes, learned at 265–290, going green at 305–330, going grey at 325–350. Required for Runed Arcanite Rod.
Large Brilliant Shard: 33 recipes (Classic, 29 in WotLK), learned at 290–300, going green at 322–325, going grey at 340–340. Required for Runed Arcanite Rod. One recipe is 315-315. Also used in three Tailoring recipes, included in those counts of 33 and 29.
Illusion Dust: 19 recipes (15 in WotLK), learned at 270–300, going green at 310–340, going grey at 330–360. Required for both Runed Arcanite Rod and Runed Fel Iron Rod; both need 10. Can be mainly skipped except for the rods, it's hard to get and expensive.
Nexus Crystal: In Classic, and end-game material, 300, 11 enchants. In TBC and after, only four glove enchants (300-340) and a transformation spell into a Small Prismatic Shard. Also used to Blacksmith Sageblade.
Arcane Dust (TBC): Over 30 recipes, used in basically all TBC enchanting. Earliest use at 300-340, needed all the way to 375 – unless one skips to Wrath enchanting.
Lesser Planar Essence (TBC): Earliest use at 305-315-330-345, last at 330-340-355-370.
Greater Planar Essence (TBC): Earliest use at 300-310-325-340, used all the way up to 375, in the TBC endgame.
Small Prismatic Shard (TBC): Earliest use at 300-310-325-340, last at 350-360-370-380.
Large Prismatic Shard (TBC): Earliest use at 325-335-350-365, last at 375, in the TBC endgame.
Void Crystal (TBC): Burning Crusade end-game material, used not only in Enchanting (360–375) but Leatherworking, Blacksmithing, Tailoring.
Infinite Dust (WotLK): Like 60 recipes, used throughout WotLK. Earliest use at 350.
Lesser Cosmic Essence (WotLK): Earliest Enchanting use at 360.
Greater Cosmic Essence (WotLK): Earliest Enchanting use at 385.
Small Dream Shard (WotLK): Turned into normal-size Dream Shards.
Dream Shard (WotLK): Earliest Enchanting use at 410.
Abyss Crystal (WotLK): Earliest Enchanting use at 430.