If you blinked again, you might have missed it: several days after Apple released an update to the iPhone OS 3 beta, hackers have already jailbroken the OS 3 beta 3 release.
A new version of QuickPWN for Windows only (direct download link) has been released. This version should work with all versions of the iPhone or the iPod Touch. We have not yet tried the jailbreak, but our sources have not reported any trouble with the hack. (As usual, however, download and use QuickPWN at your own risk.)
Jailbreaking is competitive in the hacking community. The Dev Team, the favored jailbreak provider, has an opinion and some words of warning about hacks like this.