I recently discovered WGBH Radio's Bach Minutes. They are 5- or 6-minute long audio clips on interesting aspects of J.S. Bach and his music. Delivered by Benjamin Rowe, the Minutes touch on such topics as Music and Math in Harmony: The Art of the Fugue, Pablo Casals and the Cello Suites and many more.
As with everything WGBH produces, these are well done and well worth your time. Have a listen here.