I've been using *nix for a while now. Started off with FreeBSD, moved to RedHat and have been running Ubuntu for the past few years. I have my laptop dual booting with Windows 7 and Ubuntu 9.10 Karmic Koala. What I woud recommend is go into a book store and pickup some of the Unix books they have and read through them and see which one you like best. One thing about Unix is that they keep moving stuff around so it drives you crazy.