Server 2008 Network Access Protection (NAP) is a software based solution that allows computers to be checked for compliance, then placed on an isolated network if non-compliant. How is this related to SCCM 2007? The ConfigMgr client has the NAP SHA (System Health Agent) built-in. NAP can additionally be used to remediate computers that may not have all current security updates applied before they are allowed on a designated corporate network. ConfigMgr has an available System Health Validator (SHV) role that integrates with NAP.
In working on a recent project that involved NAP Proof of Concept, we compiled a list of Server 2008 Network Access Protection references that may be helpful.