I have the need to federate a Drupal site with AppFabric Access Control Service. I have started down the road of using SimpleSAMLphp with the simpleSAMLphp_auth Drupal module to enable Federated Login. I'm not having much luck configuring the SimpleSAMLphp application and the Drupal module.

SimpleSAMLphp supposedly supports WS-Federation. I can't find any documentation on how to set it up however.

Has anyone been successful in setting Drupal up to use ACS as a federated login?

I haven't set up ACS with Drupal, but the ACS Plugin for Wordpress includes PHP code that shows how to accept an ACS-issued SWT token using WS-Federation. This might help you:

http://wordpress.org/extend/plugins/acs-plugin-for-wordpress/