iOS 4.3.1 was just released earlier today, but there’s already a tethered jailbreak available for it—which’ll work assuming you’re not using an iPad 2.
https://gizmodo.com/ios-4-3-1-update-is-live-but-just-fixes-bugs-5785806
For full instructions on how to jailbreak your iOS 4.3.1 device using the PwnageTool, head over to Redmond Pie. The folks there appear to have explained the entire process pretty well. [Redmond Pie—Thanks, Brad!]
