Untethered iOS 4.3.1 jailbreak is go with redsn0w and PwnageTool for Windows and OS X, minus iPad 2
So, if you're running an iPhone 3GS or 4 (GSM), an iPod touch third or fourth-generation, or an iPad 1 and want to get your jailbreak on, head on over to the Dev-Team blog for official links to both redsn0w (Windows or OS X) and PwnageTool. If you're an ultrasn0w user however, you best wait a little as there's a fix coming for some bugs between iOS 4.3.1 and the older basebands required for carrier unlock. Apple TV 2 owners can also get in on the action, but are limited to PwnageTool for your jailbreak needs. iPad 2 owners I'm afraid you're left out in the cold on this untethered one, as the iPad 2 requires a bootrom-level exploit to install and Apple's latest device is not susceptible to either the current limera1n or SHAtter bootrom exploits.