Looking forward to trying some of these. I usually try a tech podcast once in a while and feel like I'm working rather than relaxing. :) My favorite exercise-time podcasts have been Spycast, Film Sack, StarTalk, and Radiolab. Occasionally I'll search the podcast directory by personality so I'll find e.g. a podcast where Scott McCloud is interviewed, and listen to it, but not actually subscribe to the podcast.