This comprehensive source of information about US foundations and corporate donors is the web-based version of The Foundation Directory.
The UNH Library's subscription to the Foundation Directory Online at the Professional (all-inclusive) level provides access to:
American Political Science Association
Political science and related disciplines
Federal Sponsor and Policy Updates -- Updates from the agencies and offices themselves
Grants.gov - Grant Making Agencies
Brief descriptions of the 26 Federal agencies that use the Grants.gov portal to post funding opportunities