Couros has a link about Puppy Linux. It looks like with a few minutes one can download a CD, boot it, and then install this mini-distribution on a USB drive. It runs most everything from RAM disk, so it's pretty fast. This looks like a potentially useful way to have a computer on a USB drive so that wherever you go you have all of your files and settings with you.
A cool project would be to do something like outfit a classroom of students with these to see how their use of computers changed and whether they do stuff like, you know, actually edit and revise work that they create.
It's really small, so there's no OpenOffice, but it has Abiword, mozilla, and gnumeric. It looks pretty cool. One downside is that it wants to wipe away all the files on your USB drive to do the USB install (not necessary if you're willing to boot off a CD).