I'll recommend you some more configurable distro instead of desktop oriented ones as RedHat or Mandrake. It can be a little harder to get it running, but you will have a better control of what you have in your system.
As everything, it's matter of personal preference, and I'd choose Debian, but maybe Gentoo would be good too, but the installation may hurt if you haven't a bigger computer for compiling the sources. LFS is another option if you have lot of free time.