Redsn0w 0.9.9b8 is fully compatible with the iOS 5.0.1 Beta released to developers yesterday.
Yesterday, Apple pushed out the iOS 5.0.1 Beta to developers which has fixed numerous bugs in iOS 5 and brings the beloved multitasking gestures back to the original iPad. It was reported that iOS 5.0.1 could have been jailbroken with redsn0w 0.9.9b7, although you would need to point redsn0w to the iOS 5.0 firmware file, and the jailbreak was tethered.
Originally Posted by Dev-Team Blog
iPhone 3GS users can still have the untethered jailbreak if they have the old bootrom, and Mac users can still make their special baseband custom ISPW files using this redsn0w for iOS 5.0.1. The Dev-Team also warns that ultrasn0w will not be updated for the beta, so it's recommended that you wait until the official iOS 5.0.1 release to the public.
You can download Redsn0w 0.9.9b8 for Mac, here.
You can download Redsn0w 0.9.9b8 for Windows, here.
Sources: Dev-Team Blog