Petopia - The best website out there for choosing pets and viewing a beastiary.

Warcraft Pets.com - An awesome website dedicated to vanity/companion pets.

WoWhead - Since getting hacked, I don't trust Thottbot or Allakhazam. WoWhead is all I recommend these days.

Blizzard's WoW Website

Sere Vala - My Guild on Earthen Ring Alliance.