After the release of Redsn0w 0.9.8b1 for Mac, iPhone Dev Team has now released Redsn0w 0.9.8b1 Jailbreak for Windows iOS 5 Beta. Jailbreak is only for those who have Apple Developers account and can use the iOS 5 beta version.
Redsn0w 0.9.8b1 for iOS 5 Beta for Windows may be jailbreak the iPhone 4, 3G, iPod Touch 4G & 3G, iPad.
Unlockers should especially stay away, because the recovery iOS 5 will update the baseband (unless you use Sn0wbreeze) and ultrasn0w not been updated for iOS 5 yet.
You can follow here to step by step jail break your iPhone 4 & 3GS, iPod Touch and iPad.