CentOS, the Community ENTerprise Operating System, is a community-driven project based on RHEL (Red Hat Enterprise Linux) aimed at servers.
Okay, now I'm using Fedora 9, actually for a few weeks already.
It has come to my attention that the current development-version of Debian is making quite good progress and a new release, labelled 5.0, is scheduled for the end of this year.
Yes, sulphur! For everybody! And free!
Why? Because Sulphur is the codename of the upcoming release of Fedora, the ninth version of it.
I have tried Ubuntu many times before and I even recommended it to people (even my sister who has now converted over to the FOSS side of computing and loves it).