Free [reg-ware] eBook "Understanding Microsoft Virtualization Solutions, Second Edition" (Updated for Windows Server 2008 R2) now available
"Learn about the latest Microsoft Virtualization technologies, including Hyper-V and Windows Azure. Download Understanding Microsoft Virtualization R2 Solutions, written by industry expert Mitch Tulloch along with the Microsoft Virtualization team.
Doesn't say how long it's going to be available for, so if you're interested, or think you might be in the future, grab it now.
As you can see, this book covers the whole gambit, from presentation, to application, machine and cloud virtualization.