I hadn’t really heard about CentOS yet, but have been seeing it offered on hosting packages. Looks pretty cool…

www.centos.org – The Community ENTerprise Operating System

CentOS Overview

CentOS is an Enterprise class Linux Distribution. It is a rebuild of Redhat Enterprise Linux that conforms fully with Redhat’s redistribution policy and aims to be 100% binary compatible. (CentOS mainly changes RHEL packages to remove RedHat branding and artwork.)  CentOS is free, however, we ask for a small contribution.  CentOS is a project of the cAos Foundation.

CentOS is developed by a small but growing team of core developers.  In turn the core developers are supported by an active user community including system administrators, network administrators, enterprise users, managers, core Linux contributors and Linux enthusiasts from around the world.
CentOS has numerous advantages including: an active and growing user community, quickly rebuilt, tested, and QA’ed RedHat errata packages, an extensive mirror network, developers who are contactable and responsive, multiple free support avenues including IRC Chat, Email Lists, Forums, a dynamic FAQ, commercial support is offered via a number of vendors.