America's Most Promising Social Entrepreneurs 2011

When Jonathan Jackson started Dimagi, a software firm that makes open-source tools to improve health care in underserved communities and developing countries, he wanted to help people in need and create a sustainable, profitable company. Last year, the 20-employee Charlestown (Mass.) business got certified by B Lab, a nonprofit that promotes socially responsible business to show fellow entrepreneurs that businesses can tackle social ills. "Growing up, I thought the way you did that was go get rich and then donate your own money," says Jackson, 30. "I didn't realize there was this industry behind it."

Dimagi is one of 25 ventures that Businessweek.com selected from reader suggestions to profile in our third annual roundup of America's most promising social entrepreneurs. The companies make products ranging from software to compost, and sell everything from baby food and brownies to insurance and financial services. They're innovating, too: Promethean Power Systems helps developing-world dairy farmers keep milk cold long enough to reach markets, while Mia Consulting created a new model for housing low-income senior citizens. Together these 25 companies employ more than 600 people and generated $165 million in revenue last year. The median company in the group has a staff of 19 and sales of $1.7 million.