Invirt is free software for managing Xen virtual machines. Invirt powers the xvm.mit.edu service at MIT.
Evan Broder and Greg Price gave a talk about Invirt internals in December 2008; you can see the slides.
Invirt is free software under the GPL. The source repository is in Subversion:
$ svn co svn://invirt.mit.edu/trunk invirt
If you're interested in running Invirt in your own environment, feel free to contact us at invirt@mit.edu. It's not yet straightforward to install; we're working on it, and we're happy to help you set it up.
Invirt is based at SIPB, the student computing group at MIT. We welcome new contributors; check out our bug tracker for an idea of what we're working on now.
Questions welcome at invirt@mit.edu.