For articles on microfinance; search EconLit and Proquest ABI/Inform.

For books on microfinance search UIUC's Library Catalog using microfinance as a Subject Word.

Take a look at The Microfinance Gateway.

CGAP; The World Bank microfinance site; has a data section.

The International Labour Organization has a resource guide on microfinance.

USAID Microenterprise Results Reporting page posts data.

MicroLinks provides additional microfinance-related resources.