Get Started with Game Design!Activate! http://www.activategames.org/ is a site where you can not only play games, you can learn to make them, too.
Scratch http://scratch.mit.edu/ is a programming language that makes it easy to create your own interactive stories, animations and games and is used by Game Tech.Kodu http://research.microsoft.com/en-us/projects/kodu/ is a new visual programming language made specifically for creating games that runs on the Xbox.