After our Locke episode, I blogged re. this Steven B. Smith introduction to political philosophy course from Yale, but in the case of the Plato episode, I actually used these three lectures as part of my preparation and discussed them on the show:
Watch the first Plato lecture on Youtube.
Get the audio from iTunes.
As we said on the episode, Smith gets very into the literary aspects of this, such as what positions in Plato's society each of Socrates's interlocutors represent, and a great deal is also made of the first line, "I went down to the Piraeus..." and all the metaphors about going up and down towards the forms and or the gritty material world throughout the dialogue. Also, as Dylan commented on the episode, per my recommendation, you might want to get the audio version and listen to it on double speed, as he'll then sound like he's speaking at a normal conversational speed. The man is a slow talker, to be sure.
Note also that he, like us, didn't try to treat more than the first half of the book, even though the allegory of the cave that comes later is the most famous part. To hear more about Plato's epistemology, which is what that section is about, check out our episode on the Theaetetus and the Meno (at the time, I did look at those portions of the Republic to try to bring some of that epistemological discussion in too, though it's not dealt with in any detail on that episode).
For a few more thoughts on Smith's course, see my recent openculture.com post.