Well, the first thing you want to find out is what is it going to be used for? Will it host the website for your business (if this is what it's for)? Are you planning on doing any database stuff? Do you want to use it to store files for all the users? Once you have a plan set up for what you want done with this server, you can start taking steps on what server apps to use.
• Apple iMac G5 17" (2 GHz G5) - Mac OS X 10.5.8/Ubuntu 10.04
• Asus Eee PC 901 (1.6 GHz Atom N270) - Fedora 13
• Apple Macintosh Quadra 650 (33 MHz MC68040) - Mac OS 8.1
• "JHVH-1" (2 GHz AMD Athlon XP 2400+) - Slackware 13.1