xGestures allows you to use mouse gestures in all aspects of your Macintosh computer. You can define gestures for individual programs, or for the whole computer, and map them to useful functions like closing or minimizing windows, switching or launching applications, picking menu items or performing keystrokes, triggering Exposé, and much more!

Limitations: 15-day trial.

Requirements:
OS X 10.3-10.6
Universal Binary