EPEL is a volunteer-based community effort from the Fedora project to create a repository of high-quality add-on packages that complement the Fedora-based Red Hat Enterprise Linux (RHEL) and its compatible spinoffs such as CentOS or Scientific Linux.
http://fedoraproject.org/wiki/EPEL
su -c 'rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-2.noarch.rpm' ... su -c 'yum -y install foo'