I've been playing with distros lately. I have a couple dozen of them and have 5 of them currently installed, each on a separate hard drive on one of my play computers. I would tend to categorize them as 1. simple and friendly (Linux Mint, Xandros) 2. middle of the road (Ubuntu, Suse, Fedora etc.) and 3. for experts only (Slackware, Gentoo.)
First you need to decide which category fits you best and then you can look into things further. I happen to like Linux Mint with KDE among the simple, friendly distros. Linux Mint is actually based on Ubuntu and uses the Ubuntu repositories. It is really simple to set up and get going and has good documentation. It's a great place to start with Linux.
Ubuntu takes a little more effort to get going but it is really very well supported thanks to its popularity. It is my favorite distro in the middle of the road category. It is easier than most typical distros for managing a network and that's important to me. If I didn't use Ubuntu I would probably go with Fedora and Gnome, personally. Harder to network but pretty nice in other respects.
In the advanced category I like Gentoo. It isn't as bare-bones as some of them and can be used without dedicating yourself to a life of Linux study and practice.
