iH8sn0w (@iH8sn0w) has just released a video in which he demoed iOS 4.3 multitasking gestures on his iPod Touch 4G. Currently the only possible solution to enable multitasking gestures without jailbreaking iDevice on iOS 4.3 is through Xcode which will cost you around 499$. Other possible solution is to jailbreak and replace some PLIST files in Preferences.app through SSH.
As told in the above video, iH8sn0w will push another beta of Sn0wbreeze 2.3 which will enable multitasking gestures option in the Settings app. If you do not want to wait for the 2nd beta and have already jailbroken your iDevice on iOS 4.3, proceed to this tutorial to enable these multitasking gestures manually through SSH. In anycase, we will let you know as soon as Sn0wbreeze 2.3b2 is available for download. Stay tuned!
Update#1: Download Sn0wbreeze 2.3b2 for iOS 4.3 Jailbreak [Fixes iBooty, MobileSubstrate & iPod Touch Sleep Bug]
Update#2: iBooty 2.1 Released: Fixes Waiting for iBSS Isse on iPod Touch 4G/3G
Update#3: Download Sn0wbreeze 2.3b3 to Fix iPod Touch 4G iBooty Issues