The illustri-notorious Dev Team has blogged about Jailbreaking iPhone OS 2.2.1, released by Apple earlier this week.
Simple version: You can now Jailbreak, if you haven't already upgraded to 2.2.1 via iTunes, are using a Mac, aren't affected by the OS X 10.6 DFU-mode bug, and -- if you want to keep using yellowSn0w for unlock -- are happy to spin your own custom firmware.
Complex version: involves closing the barn door -- see here.
(For community-based jailbreaking advice and support, please check out our Jailbreak Central Forum)
Hopefully an easier solution will surface when the Dev Team has spent more time hacking away at iPhone OS 2.2.1. Until then, the cat and mouse game continues!