GameDev.Net
Offers articles, columns, resources, news, and links.

So You Want to be a Computer Game Developer
Eight chapter online book.

GameCreators
Site includes a list of links to many different game editors and articles.

Johny's Ranting on Gaming
Personal opinions and commentary on game design, especially multiplayer games.

Game Depot
A website with discussion forums for discussing game design. 3D topics and others.