Learn About Congress is a site sponsored by Indiana University that has several videos and animations (with text and audio support) designed to show how the United States Congress works (or, at least, how it’s supposed to work).

Most of them would be most appropriate for Intermediate or Advanced students, but one or two of them might be accessible to high-beginners.

I’ve placed the link under the Citizenship category on my English Themes for Beginners/Early Intermediate.