Seeing as Apple seeded iOS 5 beta 6 today, a lot of users want to know if they'll need to wait in order to update and re-jailbreak. The answer to that is no. Go ahead an update. The existing version of Redsn0w for Mac and Sn0wbreeze for Windows will work just fine. I've confirmed this working on a 4th generation iPod Touch. iDB has confirmed it working as well.
The process should be the same as previous versions of Redsn0w and Sn0wbreeze. Just use the new beta 6 firmware file in place of beta 5 or earlier.
As always, remember that not only is iOS 5 in beta, these jailbreak tools are also beta. Unless you're a developer or jailbreak developer, I'd probably hold off on doing this. Not all regular apps are compatible with iOS 5 let alone jailbreak apps. So be advised to proceed at your own risk.