Slackware Linux 10.
Slackware is fast, stable and secure. Its got a great selection of apps on the cd, your choice of gnome or kde.. no linux distrobution is as fast or stable as Slackware. Gentoo's reckless use of optimizations and poorly tested ebuilds makes it unstable. Red's unsecure, bloated... SuSE is .. commerical, and the free Versions are incomplete. Debian is ugly, crufty and messy. I've been using linux since '94, and I learned on slackware and its the best thing, because Slackware doesn't hide the OS from the user with a bunch of (usually unstable) GUI tools. When you learn slackware you can say you've learned linux, with redhat or suse your just learning redhat or suse.
Course, all of the above is just my opinion
--SD