I just learned of this podcast a couple of weeks ago: Ultrarunner Podcast.  I've listened to 4 or 5 episodes, and the guys do a great job.  My favorite interviews so far are Jimmy Dean Freeman and Sunny Blend, Sport Nutritionist, both of which I intend to back and listen to again.  Just started listening to the interview Dr. David Hannaford, elite sports podiatrist and ultra runner.  So far, also an excellent interview.