If you've spent most of your time working on Windows 95 and its successors, you may have forgotten that there was a time when you could fit a program on a floppy disk and carry it with you. These days most software by default leaves pieces of itself littered around a computer. Besides, they're too big for floppies.
Now, the cheap availability of USB "keychain drives" has enabled larger amounts of storage that can be carried around. (I dare say the flash memory is probably more reliable than a floppy too.) So why not install, say, a web browser, so that all cookies, history, etc. etc. are saved on the removable drive?
These people have done it.
However, their product costs roughly twice what you could get equivalent blank USB drives for. So now I have to wonder, how feasible is it to set up the same kind of deal on your own, starting from a blank drive? We'd want Mozilla--probably possible. If you wanted IM clients, not sure if those would be happy in completely separate disk space. For the really paranoid, throw in GPG and ssh for tunneling.
Hmmmmm.