World of Warcraft
Official site of the most addicting game ever.
www.worldofwarcraft.com

Thottbot
Like Google, but for Warcraft!
www.thottbot.com

Allakhazam
WoW Item lookups include median auction prices, screenshots, etc.
wow.allakhazam.com

CT_RaidAssist
Allows healers to track HP in large raids. Get ct core and ct_raidassist from link below.
http://www.ctmod.net/downloads.ct

Ventrilo
Pick up Vent for voice gaming. Get the server IP and password in game.
http://www.ventrilo.com