I'm working in .NET 3.5, which unfortunately has no built-in support for SAML 2.0, but there are many third-party libraries and references to build your own support for it.
Here are some of the best links I have found for learning SAML.
- Google's introduction to SAML SSO
- SAML on Wikipedia
- SAML 2.0 on Wikipedia
- Official specs and documentation for SAML