I've taken to removing many of my podcasts - they just end up piling up like unread newspapers and I start to feel bad about not getting around to them.
However, one that I've found has blown my mind with every episode is the feed of lectures from last year's Pop!Tech conference.
Almost every presenter has had amazing new things to say about disparate fields - some of which I never knew existed. Gigapixel photography. Deep sea exploration. Artificial evolutionary life. Private space exploration. It's all good.