RedHat, Mandrake, or SuSE will all be fine if you just wanna get it up and running as easially as possible.
Debian and Gentoo are both excellent distro's if you wanna learn a bit about how stuff actually works, and dont mind getting your hands a little dirty, but if you go this route, READ THE INSTRUCTIONS CAREFULLY!
Then read them again, then you can begin
Not to say that you don't need to read the instructions when using the other distros, only they tend to help you a bit more and be more forgiving, while Debian/Slack/Gentoo will always assume you know what you're doing, nad assume you're doing it for a good reason, so if you do something stupid, they won't stop you.
I find it hard to recomend Slack to anyone, seeing as it lacks a half decent package management system or ports system, compiling your own from tarballs is fun for a while, until you have a system cluttered with all kinds of software and you feel the need to clean it up.