No install distro :
http://www.knopper.net/knoppix/index-en.html ( dvd or cd version ) you don't need to install it , it's a live distro ! great , lot of apps and test environment , you can use it as a OS rescue
Best ( imho ) install and user friendly :
Suse professional 9.3
For your start in linux world you can try mandriva too ( ex mandrake ) , pnp , user oriented ... for newbie
http://www.mandriva.com/
if you ask to a "pure GNU | HURD " user about which distro use :
www.debian.org
Lot of distro reviews :
http://distrowatch.com/
If you want to test linux as a fi