Courtesy of a tip from Neville Hobson, I learned that Scott Kingery at "TechLifeBlogged" has released a version of Windows Live Writer that works off of a USB drive. As Scott writes:
This past February I posted a launcher for Windows Live Writer so that you can take it with your between computers and retain all your settings. Today I am releasing version 2.0 of the Launcher. Much has changed with Windows Live Writer and I have learned some new techniques for making it portable. This is a much cleaner implementation and it plays better with Windows Vista.
I don't personally have a real need to be able to do this, but I do think it's a cool idea. I like the idea of being able to use WLW on any given machine. Fun stuff!