From 10 Hours a Week, $10 Million a Year - New York Times

Quite a return-on-time-investment...

Mr. Frind built the Plenty of Fish Web site in 2003 as nothing more than an exercise to help teach himself a new programming language, ASP.NET. The site first became popular among English-speaking Canadians. Popularity among online daters in many United States cities followed more recently, and with minimal spending on advertising the site. According to data from comScore Media Metrix for November 2007, Plenty of Fish had 1.4 million unique visitors in the United States. In December, Mr. Frind said, the site served up 1.2 billion page views, and page views have soared 20 percent since Dec. 26.

From 10 Hours a Week, $10 Million a Year - New York Times