the mulituser Xtra is still available form Macromedia, but supposedly it really sucks. i looked at it when i was working on a networked video project (gethyper.com/triptych), but i went ahead and used MAX and Open Sound Control. i wish i had used PD because it would have been much easier to borrow 3 PC's and instead of hunting down several G4's.
check out OSC at http://cnmat.CNMAT.Berkeley.EDU/OSC/ and there are packages for PD and Flash.
-alex
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