BetterTouchTool lets you define tons of gestures for your Macbooks Trackpad, your MagicMouse and your MagicTrackpad. In addition to that it brings lots of new stuff to MacOS like Windows 7 like window snapping, window switchers etc.
BetterTouchTool is a must-have because it combines so many useful utilities. I’ve set Four Finger Swipe Left to Maximize Window Left and Four Finger Swipe Right to Maximize Window Right. Perfect. Gesture-based window management is just the beginning. You can map custom keyboard shortcuts to touchpad gestures: pretty much anything can be summoned with just a swipe.