Those that recently upgraded to iOS 4.3.1 and wondering about a plethora of wonderful free and paid apps banned by Apple, such as user interface enhancements and skins, could consider the latest jailbreak that leverages the new PwnageTool 2.0.1 by the iPhone-Dev team is now possible on Mac, and Sn0wbreeze on Windows.
There're two types of jailbreak: Tethered and untethered. The former requires you to tether your device to a computer each time it's restarted and the latter does not. This one's a tethered jailbreak and in very early stages so it's not for the faint-hearted.
RedmondPie has some handy guides that you can follow for all iOS 4.3.1 devices on Windows, for iPhone 4 on OS X, iPad 1 on OS X, iPhone 3GS on OS X, and iPod touch 4G and 3G on OS X.
All iOS 4.3.1 jailbreaks are still tethered, meaning you'll have to jailbreak your device after every reboot. An untethered jailbreak is slated for release sometime in the next week -- but 4.3 was meant to have an untether, too, and that never emerged.
In addition to a Mac, you will need the following: