A new E-Book : "Understanding Microsoft Virtualization Solutions" is available for free from Microsoft Press. This 15MB E-Book is over 400 pages long, so it is quite comprehensive. It covers all current Microsoft Virtualization technologies even the newest, such as the Microsoft Enterprise Desktop Virtualization (MED-V), and VDI. Definitely a worthwhile addition to your library.
Sign in with your Windows Live ID at http://csna01.libredigital.com/?urmvs17u33 to download the book.