Sample .NET code for a SAML Identity Provider

ComponentSpace claims to have example code for an Identity Provider and a 30-day trial, so you could at least look at the code.

Not really an example of code for an Identity Provider, but CodeProject has a good article on Performing a SAML Post with C#.

We had really good success with the OpenSource library that KentorIT has produced. They give you all the tools you would need to roll your own. Including a stub identity provider that we were able to use as a test & basic auth services.