Finally, this very cool tool created by Nelson Araujo is available as a free download from Microsoft (it was demo'd last year at TechEd in WINIL401). VSDM manages a virtual library of templates and ISO images and provides a streamlined way to manage and deploy virtual machines. Administrators can configure VSDM to allow non-administrators to create and manage their own machines without impacting other users' machines, or even being able to view them. This is a "must have" tool if you manage a large number of virtual machines or need to frequently recreate images based on a master image (template).
For lots of good information and support for using the tool, see Nelson's blog: http://blogs.msdn.com/nelson_araujo/archive/category/9970.aspx. For some draft installation instructions, see Paul Adare's blog: http://www.identit.ca/blogs/paul.