If you like configuring linux and figuring out how it works, I'd recommend slackware. After install, it drops you into the shell and lets you have all the fun you can handle :) But seriously, Slackware is a great linux learning tool. It lets you install as little or as much as you want. It's rock solid. And, it doesn't use any wacky package management system, you can use tgz "packages" or compile straight from source. Yea, it can be a bitch with dependacies, but at least you know exactly what you are installing.