Gamasutra	http://www.gamasutra.com/
GameAI.com	http://www.gameai.com/
Site devoted to artificial intelligence for games.
Game Developer Magazine	http://www.gdmag.com/
Game Development Search Engine	http://www.game-developer.com/
GameDev.Net	http://www.gamedev.net/
I Have No Words & I Must Design	http://www.crossover.com/~costik/nowords.html
Mu's Unbelievably Long and Disjointed Ramblings About RPG Design	http://www.mu.ranter.net/theory/index.html