[FireBeyond]

CentOS is a clone of RHEL - there is work involved in running the build systems, mirrors, de-branding and such. It is intended for those who want to use RHEL - personally, non-profit, etc., who just cannot justify the support licensing of RHEL.

Fedora, on the other hand, is Red Hat’s “next generation”. Software packages have a change to mature, be soundly tested and stabilify there before being introduced to RHEL, to give those “enterprise” users a fair degree of security on system stability, at the expense of a slow lead time (for example, one of my employers still recommends RHEL 5.x, which is “current”, though 6.x is out. RHEL 5.x uses Kernel 2.6).