World of Warcraft Community Site - Official Blizzard WoW site.

Thottbot - Information about quests, items, zones, NPCs, and just about everything else. Best place to go if you need information about a quest.

Wowwiki - Information about everything.

Allakhazam - Huge WoW data_base_.

Ten Ton Hammer- Lots of guides!

Chat Command Glossary

World Map - Interactive Flash map shows cities, towns, flight paths, instances, and battlegrounds.

MapWow.com - World of Warcraft maps using google maps api. Filters for showing herbs, ore, travel paths, etc. Very cool!

Addons @ curse.com - Lots of addons.