A few sites I find useful:
As stated above, profession levelling guides and mining routes.
http://www.thenoobschool.com/worldofwarcraft/
Quick lookup for popular Talent builds, enchants, gemming and reforges.
http://www.wowpopular.com/
Detailed lookup for talents, spell rotations etc.
http://elitistjerks.com/forums.php
WoW lore and background stuff.
http://www.wowpedia.org/Portal:Main
Addons.
http://www.curse.com/addons/wow
Death knight levelling advice (I liked this a lot)
http://considerit1.wordpress.com/2010/1 ... edemption/