Wikipedia
RepoForge
RepoForge (formerly RPMforge) is a repository of software packages for Red Hat Enterprise Linux and its derivatives like CentOS and Scientific Linux. It provides many packages in the rpm package format to these distributions.
RPMforge also had many RPM packages available for old products like Red Hat 8 after these products were no longer supported by their vendors. You can still use them with package management products like apt-get and yum; up2date does not work any more due to expired SSL keys.