These sites are not all regularly updated, but they are all recommended:
NFL Game Rewind – the best $69.99 you’ll spend all year. All-22 footage plus condensed games.
Advanced Football Analytics – Great site by Brian Burke, former fighter pilot.
Anything by Greg Cosell…he’s all over the place, writing and podcasts. Author of Games that Changed the Game
Grantland – Barnwell and Mays…ignore everything Simmons writes.
Football Outsiders – The first popular NFL analytics site, still one of the best. Run by Aaron Schatz
ESPN’s NFL Stats and Info – not updated nearly often enough, but some good stuff.
Chris B. Brown’s Smart Football
NFL Playbooks are available on a few sites, footballxos.com probably has the most…
“Football Scientist” KC Joyner and Cold Hard Football Facts [and Opinions] occasionally have good insights but they are wasted behind pay walls.