MySpace has done some pretty amazing things with the Robotic Developer Studio.  When they found out it contained a very powerful component, the Concurrency and Coordination Runtime (CCR), the architects built it into the architecture of MySpace, the largest .NET site in the world.  At MySpace, I met Principal Architect Erik Nelson and Senior Architect Akash Patel who walked me through how they were using the CCR.  If you have an MSDN subscription, you are a student, or you are at a qualifying startup, you can now download and use the Robotic Toolkit as part of the program.