The Microsoft Download Center (http://www.microsoft.com/downloads) has a growing number of whitepapers available concerning different aspects of Windows Server 2008. The following is a sampling of these resources at the time of this writing, but I expect that a whole lot more will be available to you by the time you’re reading this:
Active Directory Certificate Server Enhancements in Windows Server Code Name "Longhorn"
Introduction to Network Access Protection
Network Access Protection Platform Architecture
Configuring Network Access Protection Policies in Windows Server "Longhorn"
802.1X NAP Enforcement Step-by-Step Guide
Internet Protocol Security Enforcement in the Network Access Protection Platform
Cisco Network Admission ...