1. Marcus du Sautoy's 10-part, non-technical A Brief History of Mathematics, for BBC 4 Radio. Finished this one (at 2x acceleration) in two bus trips today.
2. Peter Adamson's in-progress History of Philosophy Podcast, from King's College London, which ambitiously intends to go through the entire history of the field with no gaps. I would do this myself, but I think my speaking voice is horrible, and the pace of my written history of philosophy (still on Anaximenes!) inspires no confidence.