Shamelessly stolen from here.
World Achievement tracking site (in beta until achievements go live): http://www.wow-achievements.com/
The hard ones:
the easy ones:
account wide achievements (yet to be announced)
Notable Achievement rewards:
* Ambassador - Get all 5 alliance/horde factions to exalted
* Arena Master - Complete the arena achievements
* Argent Champion - Exalted rep with the Argent Dawn and the Argent Crusade
* Battlemaster - Completing all major PvP Achievements
* Bloodsail Admiral - Obtain Bloodsail Admiral's hat
* Brewmaster - Complete the Brewfest holiday achievements
* Chef - Complete the cooking achievements
* Challenger - Arena ranked in top 35% at end of season
* Champion of the Frozen Wastes - Defeat all the heroic bosses and Naxx in Northrend
* Champion of the Naaru - Completing the old attunement to TK (must be done pre-wotlk)
* Conqueror of Naxxramas - Realm first Kel'thuzad (25man) kill.
* Diplomat - Exalted with Timbermaw Hold, Sporeggar and the Kurenai / Mag'har
* Duelist - Arena ranked in top 3% at end of season
* Elder - Talking to all of the Elders during the Lunar Festival
* Exalted - Becoming exalted with at least 40 factions
* Explorer - Discovering all zones of Azeroth, Nothrend and Outland
* Flame Warden - Completing the major Midsummer Fire Festival achievements
* Flawless Victor - Win 10 ranked arena matches in a row with a rating above 2000.
* Gladiator - Arena ranked top 0.5% at end of season
* Guardian of Cenarious - Exalted with Cenarian Circle and Cenarian Expedition
* Hallowed - Complete the Hallow's End achievements
* Hand of A'dal - Completing the old attunement to Mount Hyjal and Black Temple (must be completed pre-wotlk)
* Immortal - Within one raid reset timer, clear Naxxramas without a single death (during boss fights), 25man version
* Jenkins - Killing 50 Rookery whelps in 15 seconds
* Justicar - Exalted with Silverwing Sentinels, Stormpike Guard, and The League of Arathor
* Loremaster (title + tabard) - Complete the quest achievements in the various zones around the world.
* Love Fool - Complete the "Love is in the Air" holiday achievements
* Matron or Patron - Children's week achievements
* Magic Seeker - Realm first Malygos (25 man) kill
* Merrymaker - Complete the Winterveil achievements.
* Obsidian Slayer - Realm first Sartharion (25 man) kill
* Of the Alliance/Horde - 100,000 HKs
* Of the Nightfall - with all three twilight drakes still alive, defeat Sartharian in 10man
* Rival - Arena ranked top 10% at end of season
* Salty - Complete the fishing achievements
* Scarab Lord - Opening AQ gates
* Seeker - Complete 3000 quests.
* Shattered Sun - Completing 'A Magnanimous Benefactor' quest
* Twilight Vanquisher - Defeat Sartharian with all three drakes still alive, 25man
* Undying - Clear Naxx during a single week with no deaths during boss fights
* Albino Drake - collect 50 unique mounts
* Black Bear - Defeat the 4 horde/alliance leaders
* Red-Proto Drake - Complete all WotLK heroic achievements
* Plagued Proto Drake - Complete Naxx, Malygos and Sartharian in 10man version
* Black Proto Drake - Complete Naxx, Malygos and Sartharian in 25man version
* Violet Proto Drake - Complete all the holiday event achievements
* Skunk - collect 50 unique pets
* The School of Arcane Magic - Mastery (I believe its a book, currently unknown use) - Read the 8 books on arcane magic.
* Tabard of the Explorer - Explore Northrend
* Titanium Seal of Dalaran - Completing the Coin achievements (fishing) - vanity item, flips a coin
Some interesting notes:
At least currently we're unsure on whether the books 'school of arcane magic - ' actually do anything or just lore.