I know someone already mentioned Knoppix, but I was going to point out
that many difference flavors of Linux (so called distributions) make a
"live CD" (like Knoppix) that you can use to boot up and try a
distribution without actually installing anything. It won't work as well
as the installed distribution would, but it at least gives you a flavor of
what that distribution is like. This affords you the opportunity to try
out several with no commitment.
If you have access to a CD burner and a broadband internet connection and
know of some distributions you're interested in, you can check out this
list:
http://www.frozentech.com/content/livecd.php
to see if they offer a live CD, download and burn it, and give it a try.
You can also just try google with "live cd" and the distro name.
For instance, if you're interested in Mandriva there's Mandriva Move, or
if you're interested in Ubuntu there's the Ubuntu Live CD. I think most
distros have a live CD these days.
I also agree with what others have said, though, which is that if you have
someone who will be helping you, it's best to pick something they're
familiar with.
Good luck (I don't really think you'll need it)!
Nick
