If you really want to learn about the server side of things with linux, I would definatly get a Redhat box up and running, or trying setting up applications a bit more manual with say a base install of Slackware. You're not going to learn anything from a hand me it all distro like Ubuntu.
abecx.net runs slackware 9.1.0
07:43:28 up 698 days, 22:14, 11 users, load average: 0.18, 0.21, 0.13
Linux lmfao 220.127.116.11 #1 Sat Sep 4 14:16:24 CDT 2004 i686 GNU/Linux