Start with the coverage of Hybrid Business Models from the Skoll Foundation, sponsor of the Skoll World Forum on Social Entrepreneurship.
Then, consider this special 2009 issue of Innovations, published in conjunction with the Skoll World Forum, entitled Social Entrepreneurship: Shifting Power Dynamics, with an introduction by Jeff Skoll.
Take a look at the offerings at the Kauffman Foundation, where entrepreneurship meets the public good.
Here's an article by Kyle Westaway in the Wall Street Journal on New Legal Structures for 'Social Entrepreneurs' (subscription required).