Add a repository
E.g. http://dries.ulyssis.org/rpm
Add a file /etc/yum.repos.d/dries.repo with content:
[dries] name=Extra Fedora rpms dries - $releasever - $basearch baseurl=http://ftp.belnet.be/packages/dries.ulyssis.org/redhat/el4/en/i386/dries/RPMS
Add their public key: rpm --import 'file-with-key'
Other Repos
[dag] name=Dag RPM Repository for Red Hat Enterprise Linux baseurl=http://apt.sw.be/redhat/el$releasever/en/$basearch/dag gpgcheck=1 gpgkey=http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt enabled=1