Genre Smash with ERIC KRIPKE, presented by the Writers Guild Foundation.
I thought it was a stellar interview. He talks a LOT about SPN, and a fair bit about Revolution too. He offers a little peek into fandom, casting, the episodes he thought worked (and didn't work), some of the network hassles he went through, a ton of good stuff!
OH! And if that's not enough, the same site has a recent podcast with Ben Edlund, too: HERE.