Pwnage Tool 3.1 for Mac OS X, users can jailbreak both iPhone 3G and the first editions of the iPhone and iPod Touch running Apple iPhone OS 3.1. The tool however does not support iPhone 3GS or the second or third generation of the iPod Touch. Jailbreaking allows iPhone and iPod Touch users to run applications that are not available through Apple's App Store. The unapproved applications can then be installed through programs like Cydia and Icy. The tool was developed by the iPhone Dev-Team.
More info: DevTeam