A recent tweet from MuscleNerd has stated the new Redsn0w 0.9.8b4 has the ability to jailbreak iOS 5 beta 4 (which was released earlier today). This is a tethered jailbreak, meaning that when the device is shutoff or restarts, it loses its jailbreak.
DL Link for redsn0w 0.9.8b4: Windows, Mac
Update #4: In conjunction with iOS5 beta4 being released to iOS developers, redsn0w 0.9.8b4 is now available for jailbreak app developers. Remember, it’s a tethered jailbreak right now so you’ll need to use redsn0w to boot into a jailbroken state at each power cycle.
don't forget to thank!!.. thank you.