When the iOS 4.3 beta emerged it included 4-and-5-finger gestures for the iPad, such as pinching to return to the home screen, and swiping to reveal the multitasking tray or switch apps. Just one week later, Apple said that iPad gestures wouldn't make the cut, and indeed, iOS 4.3 was summarily released without gestures for the iPad and recently-released iPad 2.
Don't despair, however: they can be re-enabled by turning your iPad into a developer iPad by using Apple's Xcode developer tools. Our bleached and glistening cousins at TUAW originally reported that you had to pay $5 to get Xcode 4 from the Mac App Store, but our very own Samuel Gibbs found that the free-to-download Xcode 3 works just fine.
To unlock iOS 4.3's gesture controls on your iPad, download and install Xcode 3 (bottom of the page), open Xcode, connect your iPad to your PC, then Window > Organizer and press the "Use for development" button. You can also download Xcode 3 from elsewhere on the Internet if you don't want to sign up for an Apple ID.
Let us know in the comments if you successfully enable gestures on your iPad!