Federated Security Framework
One of the great issues that exist when developing solutions is the Security, and when we talk about SaaS or S+S the issue becomes a lot more complicated and so we have to use Federated Identity, and there are several ways to do this and as Frederik Chong from Microsoft and Dwayne Taylor from RDA wrote on their article Federated Identity: Scenarios, Architecture and Implementation this is not a easy issue to solve and so they show some ways that can be used, and although this is a 2006 article, it's still very interesting to read about the issues, but now the Federated Security Team is developing a framework for Federated Identity with the codename "Zermatt" that's present on the Microsoft Connect Services site, and this already have a public beta that can be downloaded and used.
For more information's about the Zermatt you can check the Microsoft Connect Services site and there are some whitepapers for developes you can read to get to know a little better this new framework, and you can also check this Matias Wolosky Blog entry and the Vittorio's blog from Microsoft that made the announcement of the framework.
This is a framework that will help a lot when developing claims-aware applications. This framework will work on top of technologies like Windows Cardspace, WCF, ASP.NET and several other to help developers and architects.