Cubicle 7 Games — The new home for the Wrath and Glory — Warhammer 40,000 RPG.
Games Workshop — For all that's official about the 40K tabletop game.
Forgeworld — For the other games of the 40K universe, such as Adeptus Titanicus, Aeronautica Imperialis, Necromunda, and others.
Black Library — Publishers of 40K novels and fluff books.
Doctors of Doom — A large site with lots of content, including character generator, homebrew collection, threats, etc.
Servants of the Imperium — A fantastic and fun web comic dedicated to 40KRP.
Please feel free to email me with any suggestions, comments, or ideas.