Civics 101

New Hampshire Public Radio began a podcast last January called Civics 101 - a refresher course on some of the basics of American democracy. You can find the list of topics (52 so far) here. Episodes include U.S. voting systems, federal grand juries, presidential pardons, church and state, how a bill becomes a law, gerrymandering About 12 min, no transcripts.
The site also has something called « extra credit » with supplementary information about the topics in the podcasts and even quizzes about the topics covered.