The early iOS 4.3 builds had a number of multi-finger ala-MacBook gestures enabled as a developer preview of what’s to come. Unfortunately, they didn’t get through in the final retail version of the software. The good news today is that they can still be enabled with a software tweak (no jailbreaking necessary).
Now you can get four and five finger sideways swipes for alternating open applications, five-finger pinch for going back to the homescreen and four-finger swipes up for accessing running apps tray and playback buttons.
To enable it you will need a MAC OS X-running computer and a $5 MacOS app. Here’s the activation instructions, courtesy of Gizmodo: