I was supprised to find that there was no RPM provided by yum for webmin; neither in the base packages or Dag repository. For anyone who wants it is is avalible using my yum repository. Add the following to a file /etc/yum.repos.d/Doylenet.repo

[doylenet]
name=Doylenet custom repository for CentOS
baseurl=http://files.doylenet.net/linux/yum/centos/5/i386/doylenet/
gpgcheck=1
gpgkey=http://files.doylenet.net/linux/yum/centos/RPM-GPG-KEY-rdoyle
enabled=1

You can now install it using the command below

yum install webmin

Accessing Webmin is as easy as going to https://server:10000 and logging in with your root account.