There is a September 2010 Labs release of Access Control Service ACS at the following link http://acs.codeplex.com/ . This ACS samples and documentation project is intended to be used with an Azure AppFabric labs portal account. The above link takes you to the home page which lists the key features of ACS.
There is a getting started section http://acs.codeplex.com/wikipage?title=Getting%20Started&referringTitle=Home if you want to dive right in, starting with creating an ACS namespace, adding identity providers, setup relying party, create rules, define signing credentials and integrate with Visual Studio.
Working with the Management Portal page http://acs.codeplex.com/wikipage?title=Working%20with%20the%20Management%20Portal&referringTitle=Documentation , this documentation covers managing ACS configuration. Provides step by step instructions on how to work with the various ACS resources available in the management portal.
A videos walkthrough page is available at http://acs.codeplex.com/wikipage?title=Videos&referringTitle=Home .
The download ACS samples page http://acs.codeplex.com/releases/view/53011 . The readme's for the samples http://acs.codeplex.com/wikipage?title=Samples .
The prerequisites page can be found here http://acs.codeplex.com/wikipage?title=Prerequisites&referringTitle=Home , Visual Studio 2010 any edition, .NET4 or 3.5 SP1, WIF Runtime and SDK are among the requirements.
