As the saying goes, where there's a will, there's a way - and there's always a will among the guys (and gals) at XDA-Devs. This time around, it's booting Ubuntu on the Samsung Galaxy Tab; unfortunately, though, it's not without a fair number of kinks at this point.
XDA member dviera88 discovered that the method used to boot Ubuntu on the Epic 4G also works on the Galaxy Tab (unsurprising, given just how similar the two are). He's provided a nearly 13-minute video detailing how to get it up and running and providing a quick usage demonstration. Heads-up, though: it's shot on his Epic 4G, so the video isn't great.