The mathematicians behind Baseball Reference, Pro Football Reference, and Basketball Reference are joining forces to launch a company to support their sites. All three sites were started as hobbies, but have grown to be as essential in their own areas as Wikipedia is in general. Baseball Reference was the original and motivated the creators of the other two sites, and all three of them are friends who met at math conference.
It’s nice to see the guys behind them turn them into a real business, rather than seeing them just get sold to ESPN or die because they become too much work to keep up and running on a part time basis.
The hobbyist Web site turned business is perhaps my favorite Web business model.