The RCE podcast does a special on Singularity

Brock Palen and Jeff Squyres speak with Gregory Kurtzer about Singularity a container solution for HPC and research environments. Singularity allows a non-privileged user to "swap out" the operating system on the host for one they control. So if the host system is running RHEL6 but your application runs in Ubuntu, you can create an Ubuntu image, install your applications into that image, copy the image to another host, and run your application on that host in it's native Ubuntu environment.