Answer
Last Updated: Feb 24, 2017     Views: 52

Here are some excellent resources:

Foundation Directory Online
Updated weekly, Foundation Directory Online provides the most accurate details available on U.S. funders and their grants. Over 100,000 U.S. foundations and corporate donors, over 2.4 million recent grants, and over half a million key decision makers.

Pivot (formerly Community of Science) 
Grants offered by a wide variety of funding sources from all over the world, including federal and regional governments, foundations, professional societies, associations, and corporations,

Grants.gov
Single access point for over 1000 grant programs.