Continuous Integration with Team System - http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnvs05/html/ConIntTmFndBld.asp
Extending Team System - http://www.microsoft.com/technet/itsolutions/msit/deploy/vstsextendtcs.mspx
James Manning's Team System blog - http://blogs.msdn.com/jmanning/ (good source for code and API samples)
Mickey Gouset (blog) from Team System Rocks - http://teamsystemrocks.com/blogs/mickey_gousset/
Team System Admin Tool - http://www.gotdotnet.com/codegallery/codegallery.aspx?id=cea30722-cd0a-4ef4-9c75-a5a5e4932b05 (add users to all levels in Team System)
A blog on Vertigo Software - http://blogs.vertigosoftware.com/teamsystem/default.aspx (good source for a hodgepodge of things)
List of Team System blogs on MSDN - http://msdn.microsoft.com/vstudio/teamsystem/community/blogs/default.aspx
Web Interface for defect tracking - Power Tool from Microsoft