The iPhone dev team have posted a tethered "redSn0w" Jailbreak for the 2nd generation iPod touch. They are providing it with expert-only instructions, and a strict warning that they won't be providing ANY support for it (if you ask for help, it means you shouldn't be using it, and they'll literally ban you from their site).

However, they also say they're working on an un-tethered Jailbreak, which will hopefully be both much easier to use, and enjoy some level of support.

If you're a supra-command-line ninja, however, and absolutely can't wait, go get it now...