I had heard that WD40 can damage bike parts, although Sheldon seems to think that
you can make do with it.
badmother, that's hilarious! Sheldon does have an article on cleaning. I'm gonna do this:
http://www.sheldonbrown.com/chains.html#cleaning
Thanks, everybody!
Edit: There's also an article on
extending chain life with hub gears or singlespeed bikes.