This is an audiobook recording of Bertrand Russell's chapter on Plato's Republic, contained within his "History of Western Philosophy" (1945). Narrated by Geoffrey Sherman.

A philosophy podcast, The Partially Examined Life, held a detailed discussion of Plato's Republic, which can be found here:

http://www.partiallyexaminedlife.com/2011/07/11/episode-40-platos-republic-what-is-justice/