Red Hat recently launched their new OpenShift PaaS service based on their acquisition last year of Makara.
Enterprise customers, however, still have more complex requirements, including hybrid in-house/hosted infrastructure, and integration with specialized hardware appliances.
Managing complex infrastructure is increasingly being automated using tools like Puppet and Chef. However, one of the limitations of Chef is that it does not install and configure the OS: for Fedora, RHEL or CentOS I have discovered and started using BoxGrinder.
It appears that BoxGrinder was being nurtured by JBoss to complement their PaaS development prior to the Makara acquisition. First BoxGrinder was used last year by a JBoss project called CirrAS that created JBoss AS 6 cluster appliances, and then that appears to have segued along with Cooling Tower into SteamCannon, a Ruby based JavaEE PaaS framework. Publicly available artifacts from both these projects remain, but now we must wait for OpenShift to be open sourced.
A requirement of projects like CirrAS and SteamCannon has been writing specs to package JBoss into RPMs. This was done previously by a JBoss employee contributing to the JPackage project but at last Red Hat is finally packaging JBoss AS 7 into Fedora.