Hey, tsc - now that you mention it, what do you think of Knoppix? I took some Linux courses a while back & have wanted to mess around a little at home, but don't have a sacrificial machine or the nerve to try a dual boot.
(As an aside - unapproved members can't receive or send PMs, so you'll have to converse in threads for now.)
Ah -- I saw that this morning about PMs, but forgot it.
I like Knoppix. It's a derivative of Debian, which is my favorite distribution to run on servers, but has a lot of additional hardware auto-detection stuff built in, since it's meant to run on just about any box you put it in. I've used it several times in the past when I've had a server that wouldn't boot from its own hard drive, or when I wanted to do a quick disk-to-disk copy as part of upgrading the hard drive in a system. A couple of times, I've booted it on a system, then copied the X Windows configuration file it autogenerated in order to get X working on a tricky system.
I haven't used it too much as a desktop OS, but it seems to include a good mix of tools for that. The last time I played with it, Knoppix was still using KDE as the default desktop environment, which is a plus for me, since I prefer that over Gnome. (There are versions that use Gnome, though, if you prefer that or want to try it -- search for "Gnoppix.")