I’ve listened to every single one of these and they are an excellent resource if you want to know about the origins and the history of photography. Starting with photography’s relationship with painting then Camera Obscura and then onto the invention of the Calotype and the Daguerreotype, also highlighting other breakthroughs in photography and then focusing on artists who have shaped the media.
Lectured by Jeff Curto at the College of Dupage, he has put all his lectures online for free and a blog to accompany it providing accompanying resources. Very interesting and informative but while you can find this information scattered elsewhere on the net, I think it is far more beneficial downloading these because it is all contained in a single enhanced podcast.
Also link to iTunes.