Extra Packages for Enterprise Linux (EPEL): RHEL4, Centos5 http://fedoraproject.org/wiki/EPEL
hosts some useful, extra RPMs for RHEL4 and RHEL5 distros:
mercurial, trac, steel back common lisp, rrdtool, clam av, openvpn, deny hosts, rsnaphot, pound, moin, plone, zope.
Update your yum sources (no apt repository it seems as yet) by installing the epel-release RPM (http://download.fedora.redhat.com/pub/epel/4/i386/repoview/epel-release.html
) and yum install them.
The RPMForge guys provide stable, common packages which are missing from the main repositories. The easiest way to add their repositories to your sources is by installing their latest RPM: http://dag.wieers.com/rpm/packages/rpmforge-release/
( v0.3.6 as of this writing). e.g.
rpm -i http://dag.wieers.com/rpm/packages/rpmforge-release/rpmforge-release-0.3.6-1.el5.rf.i386.rpm