My favourite talk radio out there, on the internet or otherwise, is a program called Extension 720, and it is hosted by Milt Rosenberg, from WGN720 in Chicago. It is an amazingly interesting talk show for people who like history, politics, and subject matter that doesnt involve Paris Hilton or Survivor gossip.
He has a great radio archive section too where you can listen to him and his guests on topics such as Communism spies, Alexander Hamilton, Hitler's Scientists, the rise of Ghengis Khan etc.
fascinating stuff IMO.
http://wgnradio.com/shows/ex720/index.html