Visual Studio 2010 beta 1 is now available to MSDN subscribers on http://www.msdn.com.
One exciting feature of .Net 4.0 is the inclusion of the WCF Discovery libraries which implement the WS-Discovery protocol. WS-Discovery provides dynamic service discovery with a very simple protocol. using WCF Discovery you can search for services with Find() and Resolve() and you can announce services with AnnounceOnline() and AnnounceOffline(). I'm sure WS-Discovery will trigger new design ideas around event driven, dynamically discovered service infrastructures.
Ron Jacobs has provided a good and (very) quick coding demo here http://channel9.msdn.com/shows/10-4/10-4-episode-19-Service-Discovery-with-WCF/
You can find preliminary API documentation here http://msdn.microsoft.com/en-us/library/system.servicemodel.discovery(VS.100).aspx