In their own words:
We're coining a term to describe what we do. It's called social finance. It means we want to improve the tools of financial services--investments, and loans, and so forth--by allowing people to use them to help themselves, and other people, at the same time.
Zopa is early in the process in the US but the intention is for everyday people to lend to each other.
Kiva (www.kiva.org) is also out there and just had a great article written about it Stanford Magazine. It's mission is more specific:
We let you loan to the working poor
Kiva lets you connect with and loan money to unique small businesses in the developing world. By choosing a business on Kiva.org, you can "sponsor a business" and help the world's working poor make great strides towards economic independence. Throughout the course of the loan (usually 6-12 months), you can receive email journal updates from the business you've sponsored. As loans are repaid, you get your loan money back.
According to the Stanford Magazine article about Kiva:
People are lining up. In fact, Kiva has so many lenders—more than 123,000 extending $12.4 million to some 18,000 entrepreneurs in 39 countries—that it recently limited each participant to $25 per business, “so that everyone has a chance to make a Kiva loan. After two years in operation, Kiva attracts $1.5 million a month
These are game changing stories well worth watching!
** Update: Thanks also to Guy Kawasaki for his posting "Six Lessons of Kiva" summarizing the Stanford Article 'Small Change, Big Payoff'
** Update: On a related note, Fast Company posted their 2008 Social Capitalist Awards and a list of 45 Social Entrepreneurs who are Changing the World"