21. National Football League
U.S. 2010 digital revenue: $500 million
Snapshot: The league offers football fans several subscription options: fans outside the U.S. can watch every NFL game online, while U.S.-based fans can pay to listen to radio broadcasts of games or to watch replays of games online. It also makes money by licensing content for mobile phones; last March, it announced a five-year, $720 million deal with Verizon Wireless, which now lets some subscribers live stream games and access other NFL-related content from their phones.
Key digital move in 2010: The NFL took its digital operations in-house three years ago; in 2010, it also took back control of its fantasy football site and relaunched it with an assortment of new features, including a heavy emphasis on video.
How we generated our estimate: This round figure was included in a Harvard Business Review article earlier this year.