NFL Films' Greg Cosell is now a regular guest on two weekly podcasts and I've been remiss in pointing them out. Regardless of whether or not you agree with some of Cosell's opinions and thoughts on things around the NFL, I've found that I end up learning a ton about the game of football every time I listen to one of his podcasts. I'd mention Daniel Jeremiah's Move the Sticks Podcast in this same vein, but I don't think there's a better teacher of football concepts and theory than Greg Cosell.
I've included the last month or so of podcasts - there are "preview" discussions for each week so they are dated with respect to some of the details, but honestly the philosophical, strategic, and schematic discussions that Cosell has with Doug Farrar and John Hansen make these worth listening to even weeks later.
I highly recommend giving these a listen: