There is lately a growing number of white papers and presentations available on Windows Server 2008's Hyper-V role. I wanted here to provide pointers to some of them.

Hyper-V Server 2008 Getting Started Guide (docx) & Hyper-V Server 2008 Setup and Configuration Tool Guide (docx)

Virtualization with Windows Server 2008 Hyper-V (pdf)

Hypervisor Functional Specification (docx)

Windows Server 2008 Hyper-V and BitLocker Drive Encryption (docx)

Windows Server 2008 Hyper-V Product Overview (doc)