Adding the RPMforge repositories is one of the first things I like to do on a new install. Instructions are on the RPMforge website but it is as straightforward as:
wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.3.6-1.el5.rf.i386.rpm
rpm -Uhv rpmforge*
You will then notice the repo details in /etc/yum.repos.d
This allowed me to update Spam Assassin from the 3.1.9 version in the CentOS/Red Hat repositories to version 3.2.4.
