iPhone Dev Team has announced the release of Redsn0w 0.9.6rc9 for iOS 4.3.1 untethered jailbreak. Using Redsn0w 0.9.6rc9 you can jailbreak iPhone 4, iPhone 3GS, iPod touch 4G, iPod touch 3G, iPad on iOS 4.3.1. You should note that you will not be able to jailbreak iPad 2 using Redsn0w 0.9.6rc9. Earlier iPhone Dev Team has released PwnageTool 4.3 for iOS 4.3.1 untethered jailbreak. If you are a Apple TV 2G user then you can use PwnageTool 4.3 to untether jailbreak your Apple TV 2G on iOS 4.3.1.
If are relying on Ultrasn0w carrier unlock then you must stay away because Ultrasn0w is not compatible with iOS 4.3.1. iPhone Dev Team has released Redsn0w 0.9.6rc9 for both Mac OS X and Windows. You can download Redsn0w 0.9.6rc9 for Mac OS X and Windows from the link given below.
Download Redsn0w 0.9.6rc9 for Mac OS X
Download Redsn0w 0.9.6rc9 for Windows