Dan Miller offers a nonpartisan political podcast show on which he interviews candidates of all stripes. He's a very mellow host who lets people explain their positions fully.
This Saturday, at 5 pm, he is hosting a debate with Green Party Presidential Candidates. http://www.blogtalkradio.com/millerpolitics.
The 1.5 hour show is recorded live and there is usually an opportunity to call in and ask questions. You can also listen to the show anytime afterwards.