General WoW Forums

• Blue Tracker – All CM responses on the official forums
• MMO-Champion - mmo-champion website
• Elitist Jerk Forums – Theorycrafting and add-on talk
• Arena Junkies Forum - Arena PvP discussion

Leveling

• Jame?s Alliance Leveling Guide
• Jame?s Horde Leveling Guide
• Where to Level - Level ranges for zones and instances

Raiding

• Bosskillers – Raid strategies
• Tankspot- Boss strategies, video

Warlock

• Warlock Den – All about the Warlock

Priest

• A Dwarf Priest – All about the Priest

Roleplaying & Lore

• Tbelle?s RP Guide
• Roleplaying 101 - Warcraft RP & History
• History, Lore, and Encyclopedia – Official Site
• RP Made Simple

Professions

• Crafter?s Tome – Recipe lists and leveling guides
• Tailoring Leveling Guide – Quite thorough

Equipment & Item Sites

• Loot Rank- Gear recommendations based on stats
• Kaliban?s Loot List – Simple gear lists
• Wowwiki?s List of Enchants & Augments – By slot
• SimulationCraft Trinket Rankings – Caster trinkets
• Caster List of Consumables

Armory Data

• Antiarc?s Amory Tools
• Warcrafter.net – Character gear/stats and profiles
• WoW Reputation Calculator – How to gain that rep!
• The Armory, Comparable – Player ranking
• WoW Jutsu – Worldwide guild rankings
• Arena PvP Ranking – Worldwide rankings

Statistics

• Warcraft Realms – Character, guild, and realm info
• The Daedelus Project – The psychology of MMORPGs
• PlayOn -Blog featuring the social statistics of MMORPGs
• Amory Musings – Blog on WoW Armory data mining

Patches / Game History

• Download Patches
• Changes from Live Patches to Classes – List
  
• Beta Talents - Original talent trees, pre-release

Comics

• Manic Graffiti – By Anya S.Y.
• Wowphabet - By Liz @ Spiral-Bound Sketches
• Dark Legacy Comics – By Arad Keydar