Some people here in Artinsoft is doing a great deal of work around virtualization. You should check out their posts.
I was preparing a test environment for an application and I needed to run my check in tests in several versions of windows and I found this article
which has been of great help for me in setting up a virtual test lab. I really recommend it. After you read it you will figure out great new test environments.
Like database tests. where you setup a virtual disk with your database, or diferrent images with diferent driver versions.
Good Luck!