The American Archive has over 100,000 digital clips from public broadcasting in the United States It has special collections including Firing Line and the raw interviews from a large number of documentaries.
Civics 101 is a podcast with episodes that range from 15-20 minutes about the US Government. They also have graphic organizers to help you work with your students on the material.
CPSAN Classroom works with the cable channel to provide resources dealing with public affairs, government, and non fiction books including numerous videos.