Game Maker 8 - Game Maker 8 makes it easy to create great games without having to learn a programming language or spend a lot of time. Many tutorials and resources are available, along with a lot of help from the community.
Kodu - Kodu is a new visual programming language made specifically for creating games. It is designed to be accessible for children and enjoyable for anyone. The visual nature of the language allows for rapid design iteration using only an Xbox game controller for input (mouse/keyboard input is also supported).