Microsoft just released a new feature set on top of Access Control Service (ACS). It is currently in “incubation” in AppFabric Labs. The Azure Labs are charge-free developer previews of features. They should eventually move to “production” with charge patterns.
You can see a quick (5 minutes) demo of it on Wade Wegner blog’s. Wade is a Microsoft Technical Evangelist for the Windows AppFabric.
The take away for me is that among key new features is an integration with ADFS 2.0. ACS seems to basically act as a proxy to other identity providers and simplify integration.
It sounds very promising!
[[UPDATE]] There is also a good and informative presentation on channel 9.