The iPhone dev team released the latest version of its PwnageTool for iOS 4.3.1. Thanks to the work of Stefan Esser, both the PwnageTool and redsn0w now provide an untethered jailbreak for this latest version of iOS. This untethered jailbreak is compatible with all 4.3.1 devices except for the iPad 2, which is not susceptible to either the limera1n or SHAtter bootrom exploits.
If you own an iPhone 3GS, iPhone 4 (GSM), iPod touch 3G, iPod touch 4G, iPad 1G or AppleTV 2G (PwnageTool only), then head over to the dev team's blog and download the tools to jailbreak your iOS device.
As always, follow the directions carefully and heed their warning about unlocking. If you use ultrasn0w for unlocking, you may have to pass on this jailbreak until the team updates the unlock tool to support 4.3.1.