According to a recent entry on the iPhone Dev Team website, it seems that iPhone's 1.2 firmware (which will be released to the public as firmware 2.0) has already been jailbroken. The funny thing about this bit of news is that this firmware hasn't been released yet.

In the picture you see above, you'll note that the screenshot shows different applications running on the new firmware. This would normally require a dev certificate to do normally, though none have yet been issued.

In any event, we'll be checking on this little bit of news to see what else has been uncovered about it.