How the Active Directory Replication Model Works: Active Directory

Explained in detail about how AD Replication actually works:
How the Active Directory Replication Model Works: Active Directory

Quick overview of RPC for TechNet users. Well explained in a layman’s language on how RPC works:
http://blogs.technet.com/b/networking/archive/2008/10/24/rpc-to-go-v-1.aspx

How the Data Store Works
http://technet.microsoft.com/en-us/library/cc772829(WS.10).aspx

All about Service Principal Names :
http://social.technet.microsoft.com/wiki/contents/articles/service-principal-names-spns.aspx

http://msmvps.com/blogs/ad/archive/2010/06/04/what-are-service-principle-names-spns.aspx

TechNet article on how SPN works:
How Service Publication and Service Principal Names Work :
http://technet.microsoft.com/en-us/library/cc755804%28WS.10%29.aspx

Troubleshoot Windows Server 2008 and Windows Server 2008 R2
http://technet.microsoft.com/en-us/library/dd283052%28WS.10%29.aspx
holds a comprehensive and exhaustive definitions and detailed info about all concepts in Windows Server 2008 and R2.