Game Development
C/C++ Reference - A good place for C/C++ resources, a good one to have bookmarked.
XNA Creators Club - The official MDX, DX and XNA forums are now residing here.
Drunken Coders - A good site for Nintendo DS development resources, updated frequently.
GameDev - For all your game development needs.
GameTrailers - The GameTrailers website full of (you guessed it) a whole lot of game-related videos.
GP2X UK website - The official UK GP2X website (check out the Dev and Download section).
XBDev - For all your official and unofficial XDK needs.


Software Houses

Bungie Studios - Creators of Oni, Marathon and Halo.
Lionhead Studios - Fable, Black and While 2 as well as The Movies have been produced in their walls.
SEGA - So many games to list including Crazy Taxi, Sonic The Hedgehog, The House of The Dead and Fighting Vipers.