Case helped millions of Americans get online, and now he's donating much of his wealth to developing other technologies.
He founded the Case Foundation in 1997, which focuses on using technology to make philanthropy more effective. He also started an investment firm called Revolution, which invests in startups outside of Silicon Valley, and signed the Giving Pledge.
"We share the view that those to whom much is given, much is expected. We realize we have been given a unique platform and opportunity, and we are committed to doing the best we can with it," he and wife Jean wrote. "We do not believe our assets are 'ours' but rather we try to be the responsible stewards of these resources."