This is rather new to me, but a really neat idea.  Microfinance is generally understood as a a means to help offer poor or low-income clients all over the world sustainable financial services.  Some organizations allow you to lend as little as $20 or $25.  There are a few organizations that you may like to check out that I learned about from Sustainable Works, and organization based in Santa Monica, CA who promote environmental education and action:

Note:  the explanation of each organization in quotes below came from the individual websites.

Microplace – http://www.microplace.com – “MicroPlace is a brokerage platform where you can invest in companies that are creating a positive social impact in the U.S. and abroad and that offer a financial return to you.  We connect you with organizations called issuers who offer short-term notes that you can purchase. Issuers use the proceeds to help develop communities, support women, promote fair trade, provide affordable housing, conserve land and water, promote health, support green causes, and more.  MicroPlace is a brokerage platform where you can invest in companies that are creating a positive social impact in the U.S. and abroad and that offer a financial return to you.  You can earn a 0.5 to 4.5% return on your investments, which mature in 3 months to 5 years. Interest will be paid quarterly or as otherwise noted and the principal is repaid at maturity. The minimum you can invest is $20.00.”

FINCA – http://www.villagebanking.org – “FINCA’s mission is to provide financial services to the world’s lowest-income entrepreneurs so they can create jobs, build assets and improve their standard of living.  FINCA operates in 21 countries on 5 continents, serving nearly one million clients.”

GlobalGiving – http://www.globalgiving.com – “GlobalGiving is a charity fundraising web site that gives social entrepreneurs and non-profits from anywhere in the world a chance to raise the money that they need to improve their communities. Since 2002, GlobalGiving has raised $79,709,444 from 311,153 donors who have supported 7,360 projects.”

Grameen Foundation – http://www.grameenfoundation.org – “Grameen Foundation helps the world’s poorest, especially women, improve their lives and escape poverty by helping to provide access to appropriate financial services (such as small loans and savings accounts), new ways to generate income, and important information about their health, crops and finances.”

Kiva – http://www.kiva.org – “We are a non-profit organization with a mission to connect people through lending to alleviate poverty. Leveraging the internet and a worldwide network of microfinance institutions, Kiva lets individuals lend as little as $25 to help create opportunity around the world.”