Ever since I bought my first USB key, I wondered why anyone didnt make any programs to run directly from them. While I wondered, people actually did make programs for them, and I just simply forgot about my idea.
A few months back I discovered the first program, Foxit a small nifty pdf reader, which has been sitting on my USB key ever since.
I cant remember how, but someway I was directed to a page on Metafilter, where a guy asked for these kind of programs. It was walking thrugh a goldmine reading the answers.
As suggested in the answers from Metafilter, these sites are good resources for USB ker programs: The portable freeware collection and Tinyapps.org