MuscleNerd confirmed this evening that iOS 5 beta 3 can be jailbroken using redsn0w 0.9.8 beta 1 released last month by the Dev Team. Of course, to jailbreak we need not only iOS 5 beta 3 which must be installed in the terminal but also iOS 5 beta 1 which must be used with redsn0w because that version of redsn0w only recognizes iOS 5 beta 1. I assume that MuscleNerd tested Cydia also still works without problems on beta 3, but I can't tell you anything about tweaks for now.
iOS 5 beta 1 jailbreak tutorial you have here, you follow it exactly as it is presented there, except that you must have iOS 5 beta 3 installed in the terminal.
