by Edited by Lisa A. Grimaldi | October 22, 2012

Coursera screen shotTake online college courses -- for free -- from universities like Stanford, Duke, University of Pennsylvania, Princeton, and other great schools on, a social entrepreneurship company that believes a world-class education should be available to the masses. Topics run the gamut from "Introduction to Sustainability" to "Think Again: How to Reason and Argue," and the courses include online lectures.