[ Thanks to Lyle for this link. ]
“I was directed to this great program from a random stranger on
identi.ca. I had posted a dent asking thoughts on a good Linux OS
to run on a live USB. One of the replies asked, “Why run just one?
Check out MultiSystem.” A quick search revealed the MultiSystem web
page.“Using MultiSystem I was able to install several Linux OS’s on
one 16g USB stick. Combined with Plop Boot Manager, I am now able
to boot to my USB and chose between multiple operating
systems.”