Mac OS X only: The Dev-Team iPhone hackers have released yet another update to their jailbreaking PwnageTool that supports all iPhone models running the 3.1.2 update and every iPod touch model but the third generation.
The PwnageTool still hasn't changed much in practice from the first time we showed you how to use it, so grab the download via BitTorrent or one of the mirrors and follow the step-by-step instructions if you want to ride the jailbroken train. (Also be sure to read the entire Dev-Team post to check your phone against the finer points of what will and won't work with this release.)
Pwnage Tool is a free download, Mac OS X only. Windows users, previously mentioned Blackra1n should do the trick for the iPhone OS release.