CentOS, the Community ENTerprise Operating System, is a community-driven project based on RHEL (Red Hat Enterprise Linux) aimed at servers. As it is based on Red Hat it is quite similar to it and also to Fedora in terms of installation and handling.
Unlike Fedora, the "official Red Hat community distro", it is not as up to date and can be installed without GUI without much work (I think it is possible with Fedora if you choose to customize the package-list, but with CentOS there is no need for this).
It can actually be equipped with X, Gnome or KDE in order to have enterprise desktop-system.
As at work we currently are looking into renting a dedicated server I found that many companies offer the installation of CentOS. And since I did not work with it yet I decided to give it a shot.
Installation looks pretty much like Fedora, by default the system is installed onto the logical volumes and, just like Fedora, SELinux is enabled after installation. If you decide to install CentOS with X you even can use pirut and pup, the package- and update-manager you may know from Fedora (pre-9). Otherwise there of course is still yum.
Also, just like Fedora, different system-config-* tools are available for configuration. Some of these are GUI-only, but some basic ones, like for the packet-filter and for the network, also work in the CLI.
As the system is so close to the Red Hat systems everybody used to either Red Hat Enterprise or Fedora should find his way around CentOS quickly. The use of SELinux gives additional security compared to other distributions (not that other distributions are insecure in general, I just like the additional layer of security SELinux provides) adds another factor to make it an interesting choice as server-OS.
Unlike another distro I really like as server-distro, EnGarde Secure Linux, it is based on a system many people know and thus feel comfortable with. In my opinion an important factor when installing a server.
Overall, just as I like Fedora as a desktop-system I think I may like CentOS as a server-system. The final decision on which system we will use on our server has not been made yet, but currently I have narrowed down the choice to Debian and CentOS.