iPhone Dev Team had released the beta version of Redsn0w, a cross-platform jailbreaking, unlocking and customization tool for iPhone and iPod Touch for iPhone OS 3.0 and iPhone OS 3.1.2 couple of weeks back.
They have just announced that Redsn0w is out of beta and as promised, will run on the PPC OSX, and Linux platforms in addition to Mac and Windows.