I mean "sound" in both senses: "philosophy bites" provides "podcasts of top philosophers interviewed on bite-sized topics."
I have only just begun to listen, but this site looks well worth many visits. I found it through Descartes and Sum, Ergo Cogito – known more correctly as The Cogito Argument.
A.C. Grayling on Descartes' Cogito .
Melissa Lane on Rousseau on Civilization .
John Broome on Weighing Lives .
Robert Rowland Smith on Derrida on Forgiveness .
John Dunn on Locke on Toleration .
Will Kymlicka on Minority Rights .
Jennifer Hornsby on Human Agency .
Tim Scanlon on Free Speech .
Donna Dickenson on Body Shopping .
Mary Warnock on the Right to Have a Baby .
Anthony Kenny on Aquinas' Ethics .