The announcement over at the Dev-Team's blog also provides some very useful information regarding unlocking and jailbreaking iPhones and iPod touches. It gives heads-up warnings for users in different situations, such as factory-unlocked iPhone owners, YellowSn0w users, and iPod touch owners. It covers what they should or should not do regarding upgrading to 2.2.1 and using PwnageTool or QuickPwn; the Dev-Team also details a fix for entering DFU mode when using OS X 10.5.6.
Currently the release is Mac-only, but a Windows-friendly version of QuickPwn is said to be "coming soon." You can grab the release from the official BitTorrent download. Alternatively, there are several unofficial HTTP mirrors available. The team recommends comparing the SHA1 checksums when downloading from an unofficial mirror. Given the recent string of security-related downloading incidents, TUAW cannot recommend highly enough that users download from an official source or follow the Dev-Team's security advice.
I tip my hat to the many fine folks that sent this in!