This blog post from William Savedoff of the Center for Global Development provides a list of databases that can be used for finding impact evaluations, particularly those that include studies that attribute impact to particular programs, interventions or policies and whose findings are relevant to low- and middle-income countries.
There are also a links that allow readers to either submit a different database, or, correct one of the databases on the list provided.
"[T]he idea of a searchable repository for impact evaluations is compelling. Impact evaluations are a classic public good, providing information that is valuable to anyone engaged in policymaking or program development. But for evaluations to serve this function, people have to be able to find them easily and when they need them." (Savedoff, 2013)
Savedoff, W., Center for Global Development, (2013, April 16). [Web log message]. Impact Evaluation Databases: Can You Find What You’re Looking For? Retrieved from https://www.cgdev.org/page/list-impact-evaluation-databases