A great first distro would definitely be MEPIS. It's an easy installation, it will run on live-cd, so you don't have to install it on your hard drive to try it out.
It's debian-based, but you won't run into the same permission problems that Will Smith reported in the Feb. issue of MaxPC. Debian by default is locked down tighter than a drum, but MEPIS is more geared towards everyday desktop usage.
However, once you've graduated, and you're ready to really get your linux experience going, there's no replacement for Gentoo. Portage owns you.