We've released redsn0w 0.9.8b6 to jailbreak iOS5 beta6 (point it directly at the beta6 IPSW).
Two important notes about this version:
(1) Please let your device boot normally to IOS5b6 and do a clean shutdown (slide to power off) before jailbreaking.
(2) Boot logos have intentionally been disabled for now, so you'll see a black screen on tethered boots (you can re-enable logos or verbose boot with command-line options if you really want them back).
Due increased sensitivity to abrupt filesystem shutdowns in IOS5b6, it's very important that you do a clean shutdown before running redsn0w.
You can find download links for the new version of RedSn0w here. We will be updating our tutorials shortly.