I'm posting a link to this site - both here and in the list to the left.
For those who are not UK based, this is a long-running regular feature of Radio 4. In it, the moderator, Melvyn Braqg, invites experts in all forms of scholarship from quantum physics through renaissance Italy to modern economics, to discuss a particular theme. As an intelligent layman, his job is to encourage the experts make the often arcane subjects of their expertise highly accessible.
Whenever you have an hour or so spare, and want to sit back and listen to intelligent and stimulating talk, I would recommend browsing through this archive and choosing whatever you fancy. Try something you do not think you could possibly understand and/or find interesting. You may well get a very pleasant surprise. It is a treasure chest of the history of human thought!