Wowhead If you don't know what this is...well...just go there.

Allakhazam Macros Page This is a really good starter guide to the wonderful world of macros - learn them well. They are your friend.

Allakhazam Class Forums Browse and read these as often as possible. If you find any particularly wonderful posts in here, feel free to copy the pertinent (useful) game related stuff to our guild class forums.

www.MaxDPS.com Absolutely the best (IMO) for figuring out what gear to get and cast orders, also a good dps calculator based on your gear and numbers, so you will know where you should be at on the dps meters. Its not perfect, but its really good.

WoW Armory Good for looking up someone for a pug, or just checking their spec, or finding upgrades for yourself gear wise. This is an awesome companion.

Wow Matrix Best addon updater, very handy. Get it.

WowAce Good for addons, I use wow-matrix for updates, but this place is nice to go see whats what.

Curse Addons Also good.

Wow Interface Another good site that I dig for addons.

Wow UI I like these guys too. Mostly.