I was recently forwarded some links for an IT Showcase study on how Microsoft's internal IT departement is using Virtual Server:

Whitepaper: http://www.microsoft.com/downloads/details.aspx?FamilyId=25DCB14A-03F5-434D-83F7-4D46C1675B87&displaylang=en
Web cast: http://msevents.microsoft.com/cui/WebCastEventDetails.aspx?EventID=1032276993&EventCategory=2&culture=en-US&CountryCode=US

I actually found this to be quite interesting - especially the sections on how they tackled the issue of resistance to new technology in the Datacenter.