Apparently my re-reading of Herodotus last year represented good timing. I just stumbled across the Marathon2500 Project: "Commemorating the 2,500-year anniversary of The Battle of Marathon. Free phone/web-based lectures, reading groups & more".
While I have missed the lectures by Paul Cartledge, Peter Krentz, Victor Davis Hanson, and Thomas Harrison, the podcasts are available at the site.
Coming up over the next few months are lectures by Dean Karnazes, Thomas Scanlon, Robert Strassler, and John Marincola.