Pat Patterson blogs on the the Project Concordia workshop held at RSA 2008 that shows SAML 2.0/WS-Federation single sign-on from a service provider to an identity provider. The identity provider authenticates the user via a managed information card and sends claims from the card to the service provider as SAML 2.0 attributes. Note that not every combination of SAML 2.0/WS-Federation SP, IdP and Information Card STS completely works, but enough that the approach was proven.