The iPhone DevTeam blog has released the development sources for their tool xpwn version 0.3. This tool is the firmware 2.0 version of the team's "cross-platform jailbreaking library/command-line utility". The team claims it has been tested on Linux, Windows XP, and Windows Vista for both the iPhone 2g and the iPhone 3g.
Before you go crazy jailbreaking, realize the following coming straight from the iPhone DevTeam guys:
Being a suite of command-line utilities, this release is meant primarily for developers. While you can certainly jailbreak (both 3G and first-gen) and unlock (first-gen) with it, it’s not really something you want to try without reading the lengthy, detailed README. If you don’t have the patience to do that, this release is not for you.
It will be interesting to see how many people choose this route. You can find the development sources at github