For news and patch information, the official websites are pretty good actually:
The official US WoW site
And
The official EU WoW site
As mentioned above, wowinsider and warcry are good sites too. Also, Stratics and Vault are both good MMORPG networks but I was not visiting them regularly enough lately to tell if they are still that good.
For in-game data, info about quests, items, maps, NPCs etc I really like wowhead
Check around all these and see what you like best.
