I'm a little late to this thread I think... anyway, here goes; I recommend using Debian Lenny as a first distribution. Debian is a very stable distro, and it's great to start with. Some people recommend using Ubuntu, which has a Debian base. Debian has all the similarities people look for in Ubuntu (apt-get, synaptic, gnome, etc.). It is a great distro, especially for stability. The reason I think it is a good start is because it's quick to get up and running, and good to get comfortable using linux with. Eventually you will get more daring and want to do "newer" things. Debian provides the stability to get used to things, and the challenge of learning to upgrade, fetch dependancies, and compile things from source. It is a little out dated, so when you start getting more daring then you have to do system stuff to bring it up to date. These things are easy to find online because debian has been around for a while. Id probably start with a vm, move to dual booting or a kvm switch, and then eventually go to an install. I use gentoo now, but I have tried out several distro's.
