When I started with Linux, I decided to go with Gentoo. People will tell you that it is not user friendly, and, it certainly is not for the timid. But, it has some of the best, if not the best, documentation there is and the community, from IRC to thier forums, are so newbie friendly. You will learn more about linux just doing an install with Gentoo than you will running Mandrake for a year, IMHO. I am not putting down Mandrake...it just seems to me that if you want to point and click, you might as well remain with windows.
I am now running Debian via Mepis and I must say that that is not a bad choice either. It is newer and installed off a livecd, which would enable you to play for a bit before you commit. When your ready, the install is about as painless a debian install anyone ever thought of. The Mepis community is growing and friendly for the most part. Their IRC channel is a waste of time but the forums are very active.
I suggest going with one of those. If you want to learn, throw yourself into it where you simply HAVE to learn. I gaurantee ya, you will!

And, to be honest, Mepis might be a better alternative, cause it will have Java and quite a bit of non-free software configured right out the box--think nVidia, realplayer, etc. Even Mandrake won't do that for ya, unless you buy one of their packages.
Just go to
Distrowatch and you can do some research on about each and every flavor of linux out there. Also, they will show the most up to date info for webpages and download mirrors for Mandrake, Gentoo, or Mepis.