GitHub

Entrepreneurs: Tom Preston-Werner, 29, Chris Wanstrath, 24, and P.J. Hyett, 25

Funding: Self-funded

Sharing open-source software code just got easier. GitHub is a site that brings together more than 70,000 developers who specialize in writing computer software for open-source distribution. They use the site to share ideas so others can borrow from, improve on, or add it to something else, change it—whatever. Most use the free tier of the site. Some companies, such as EMI and blogging software provider Six Apart, use the paid service to sharing internal company software projects.

Lessons learned: "People and companies like saving money," Wanstrath says. "If you help them do that, they will give you their money."

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