Back at the end of April we saw a hacker, David Wong, who'd installed Android on an iPhone 2G. At the time he said that getting it onto a 3G should be trivial, and he's managed it within weeks.
Hit play on the video above to see it in action. It's not quite as "finished" as the 2G port was - there's no audio support so far - but it can access the Web with no problems, and it can send and receive SMS messages over the cell radio. There's also better Wi-Fi support than the original 2G hack.
On the table for the next version are the aforementioned audio support, as well as improved power management and control over the backlight. Wong says: "The hope is that you should soon be able to carry around your first-generation iPhone or iPhone 3G running Android and use it just as normally as you would any other Android phone".