The podcasts are really amazing, Dan Carlin turns history into a immensely compelling story. I'd recommend Wrath of the Khans most of all. There was some crazy moments in that, like the Russian explorers finding what they thought were snow peaked mountains and were actually mountains of bone from millions of dead bodies, and the sacking & fall of Baghdad where the rivers ran black with the ink from their scrolls and tomes. One of my favorite moments in Wrath of the Khans was when a Mongolian scouting party went into Europe for the first time during the crusades and the Steppe tribes, Muslim, and Christian forces all joined together to form a unified army just to fight off these Mongolian scouts.
The Wrath of the Khan podcasts and many of the other podcasts can be found here for free, and other older/bonus ones can be bought here too:
http://www.dancarlin.com/disp.php/hharchive