Earlier this week, I attended the Social Innovation Summit 2011 in Palo Alto, which featured an impressive lineup of speakers and panelists, including current and former CXOs of major companies, heads of foundations, sports and music celebrities, and a representative from the White House. Since the conference was held in the heart of Silicon Valley, participants also included a number of tech entrepreneurs who had made their financial fortunes and were now giving back to society.

These individuals had great stories to share about their organizations’ work to impact social change, but what struck me the most was the different journey each individual has taken to become a recognized social leader.  Early in their careers, many of them started with almost nothing and lacked a vision for social change. But through their sheer passion, determination, and power of persuasion, today, they are making a difference in the lives of millions of people around the world.

The most impressive was Scott Harrison, a former event promoter in New York, who was so moved by the lack of clean water on a trip to Africa that he vowed to make a difference. He built a unique online platform for fundraising, through which 100 percent of the public’s money raised goes toward providing clean water. In the five years since his first fundraising effort, during which he raised US$15,000 by having a birthday party with 700 of his closest friends (each of whom was asked to donate US$30), his organization, charity: water, has raised US$40 million, and has funded more than 4,000 projects in 19 developing countries. These projects have provided more than 2 million people with clean, safe drinking water. Of course there’s still a long way to go to satisfy the needs of the nearly one billion people who still lack clean water in the world, but it’s a start, and Scott’s goal is to positively impact 100 million people.

Then there was John Wood, who was so struck by the lack of books for local schoolchildren he met in Nepal, that upon returning from his trek, he quit his job as marketing director at Microsoft, and founded Room to Read—a nonprofit organization that recently donated its 10 millionth book to a library that his organization started in Vietnam. To date, Room to Read has opened 12,000 such libraries in the developing world, published nearly 600 titles in languages without any written books whatsoever, and funded the education of 13,500 impoverished girls.

These are just two of the many inspiring stories of individuals who have made a difference in the health and livelihoods of communities around the world, proving that true social innovation does not require vast fortunes, but rather social inspiration to achieve important and ambitious goals.