I actually have android on my iphone 3G (as a "recovery partition"). But I was asking specifically about ubuntu; perhaps I should have been more clear.
And that android, BTW, is completely unusable - I just keep it there in case my 3G gets borked in a need-to-reinstall way (like it did two years ago).
http://www.shoutpedia.com/linux-running-on-ipad-and-iphone-c...
http://www.ifans.com/forums/threads/how-to-compile-and-insta...
http://forum.iphone.cz/viewtopic.php?f=7&t=52521
So, yeah. There's stuff out there. From what I can gather there's not much work been done recently.