Great Sites

Some site that I personally use are

WOWWIKI- It's Wikipedia but only about WOW. Its extremely helpful. I can stay on this site for hours and never get tired of reading about everything in WOW. If you need to know about anything, anyone, or anywhere in WOW look here first.

Ten Ton Hammer- A great site for learning about proffesions and classes. IT also has a ton of guides on how to power level.

ThottBot- This site has information and locations for almost EVERY item and person in them game. Extremely helpful information!

Curse Addons- Personally I think this is the best site for addons! I have almost no problems from any of the addons I have gotten from here. The descriptions are really detailed (most of the time) and they are up to date. This is where I get ALL of my addons!

I also recommend getting Cosmos from Thottbot. It's how they get their data for the site. It installs an addon for the game that gathers all the data you get. Then all you have to do is run Cosmos once in a while so it can upload the data to the site.. that's it.
When you install it make sure you set it for "thottbot only" or it will install two dozen other addons too which is a pain...

Get Cosmos here.

Petopia is an excellent resource for all the information you could possibly want regarding pets for hunters - http://petopia.brashendeavors.net/index.php

I'm constantly using www.wowhead.com and http://www.wow-europe.com/shared/wow-com/images/basics/flight/en/main/index.htm to help me with my quests