While slightly larger than the usual USBs, Chip Chick points out, the Pexagon Store-It portable USB 2.0 hard drives pack in a lot.
The 1.8-inch Store-It comes in a 60GB version for $199, or 20GB for $139, and the 2.5-inch Store-It comes in up to 120GB for $179. They all include an EZ-Touch One Button that instantly backs-up your stuff. The idea is that in age where more and more applications are tied to the Web, you no longer need to carry them with you.
Instead of carrying personal laptops for trips, you can take the more portable USB drive and plug it into any laptop at the other end to retreive your files.
The Store-It drives are compatible with both the Mac and PC (aka the guy from Dodgeball and that vaguely familiar comedy writer).