Here are just some sites and/or Addons we find helpful in Tessellate
Blizzard CS EU - Blizzard Customer Support Twitter feed for the EU. Good for server updates, technical issues and the like.
WoW Head - For all things WoW.
Curse - Great site for all the addons we use while raiding. There is also an application for Curse you can download to make updating all your current addons easier.