I first missed this New York Times article from March 17, 2008 but I don't want you to miss it. The article focused on a new book edited by North Western University Professor Weisbrod, "To Profit or Not to Profit". These cases were cited in the article: the Metropolitan Museum of Art which generates more than $96 million dollars from revenue sources like parking facilities; the Girl Scouts whose uniform sales represents 25% of annual budget; and Public Television which earns significant income from licensing fees for Tickle Me Elmo.
Professor Weisbrod's book sounds more critical than supportive, particularly because of the issues around tax exemption. Anyway, this sounds like a good read for all those who are students of nonprofit social enterprise.