I found a great post on how to get a working PaaS cloud using only open source technologies. It goes trough OpenShift, Katello, Aeolus and oVirt.

it's always fun to see what technology can do, and if we don't tinker we'll never drive vision to reality

See it by yourself: http://allthingsopen.com/2012/10/16/open-hybrid-paas/

This isn't going to be a real presentation of the aeolus project but I'm currently QAing it and I'd like to to discuss some use cases as there seems to be a lot of confusion around the cloud term these days. Firstly, what is aeolus? It is a collection of tools, you have the full listing at http://www.aeolusproject.org/projects.html

Basically it allows you to automate the build of your 'template' images …