Jailbreaking tool redsn0w has ben updated to version 0.9.8b5 and will support the iPod touch third gen, iPod touch fourth gen, iPad 1, iPhone 3GS and the GSM version of the iPhone 4. At the moment it appears the jailbreak is only for tethered devices which isn’t that really a big of a deal.
If you’re a developer and you would like to jailbreak your iOS 5 beta 5 device to tweak it and to check for bugs, redsn0w 0.9.8b5 is available for download here with the Mac version available here.