Here are some useful links on P2P:

http://www.microsoft.com/p2p (uber website, badly in need of updating)

http://www.microsoft.com/technet/prodtechnol/winxppro/deploy/p2pintro.mspx (White paper)

http://windowssdk.msdn.microsoft.com/library/default.asp?url=/library/en-us/P2PSDK/p2p/collaboration_api_reference.asp (Windows Vista p2p collaboration APIs)

peerfb@microsoft.com (email alias for questions)

http://www.thoughtpost.com/p2p.aspx (Managed Wrappers for PNRP, Graphing and Grouping)

http://mooresmind.blogspot.com (Managed wrappers from Adrian Moore on the P2P Collaboration Infrastructure)

http://www.codeproject.com/csharp/PeerNameResolution.asp (Managed project built on p2p collaboration infrastructure by Adrian Moore)