Looking for a low-risk way to invest in do-good projects like solar power for affordable housing, micro-loans for Native Americans or financial services for immigrants?

Welcome to the world of community development finance institutions (CDFIs)—a virtually invisible $30 billion-plus industry of more than 1,000 mostly nonprofit, revolving-loan funds that includes credit unions, banks and venture capital funds that serve minorities and low- and moderate-income communities.

The impact investments touch on a wide variety of areas, supporting endeavors such as organic farms and the conservation of fisheries and forests. They’re also ideal instruments for high-net-worth investors who would rather devote assets to a cherished cause rather than a traditional venture capital investment.

For example, Coastal Enterprises Inc., a CDFI that serves communities in Maine, puts a focus on funding start-ups and small businesses, particularly those that are related the region’s fisheries, farms and forests. Hodgdon Shipbuilding LLC, a business in East Boothbay, Maine, that was founded in 1816, is one example of CEI’s loan recipients. The CDFI’s funds helped the company complete the construction of a prototype vessel that serves as a tender to superyachts.

Craft 3, a CDFI that focuses on community development in Oregon and Washington states, has provided financing to a community-owned wind farm in Grayland, Wash. The 6-megawatt, four-turbine wind farm sits on 29 acres a mile from the ocean. It powers 1,000 homes and produces $450,000 in annual cash flow, which assists 2,000 working families, according to Craft 3.

“They are mining that renewable energy in ways that stick to the community that the energy is emanating from,” says Craft 3 President and CEO John Berdes.

As responsible lenders—they usually offer technical assistance such as financial literacy or business training with their loans—CDFIs can be considered a success story. Their ranks include some of the most seasoned and sophisticated impact investors in the country—investors who know how to catalyze and compound social impact.

“CDFIs are the unsung heroes of the financial crisis,” says Debra Schwartz, director of program-related investments at the MacArthur Foundation. “They were on the front lines when banks would not lend at all. And it has been their mission and ability to work with the public and private sectors that has allowed them to lead the rebuilding.”

CDFIs lend where mainstream financial institutions do not—to borrowers who are deemed to be higher risk, perhaps more fragile or smaller or earlier stage. During the recession, the delinquencies of borrowers in this credit category shot up, contributing to the domino effect that led to banks writing off loans, the collapse of the credit derivatives market and, ultimately, the Great Recession. Because CDFIs are unregulated, they had more flexibility in working with troubled borrowers and survived the crisis of 2008 far better than traditional banks. As high-touch lenders whose mission is to keep their borrowers alive as well as to get their money back, they provided extensions and restructured loans, and as a result their write-offs were lower.

“We did not have a loan-loss from any CDFI during the Great Recession,” says Dan Letendre, managing director at Bank of America, which oversees the largest CDFI portfolio in the country—about $1.2 billion of mostly loans to 240 CDFIs in 50 states and Puerto Rico. “CDFIs are very good at protecting their investors.” Letendre says CDFIs benefited from their conservative management, high capitalization ratios (an average of 38% in 2010) and first-loss equity.