Listing of all Federal Funding Agencies (with links)
http://www.ncura.edu/resources/agencies.htm

Catalog of Federal Domestic Assistance
http://12.46.245.173/cfda/cfda.html

Types of Federal Assistance
http://12.46.245.173/pls/portal30/CATALOG.TYP_ASSISTANCE_DYN.show

Commerce Business Daily
http://cbdnet.access.gpo.gov

National Endowment for the Arts
http://arts.endow.gov/

National Endowment for the Humanities
http://www.neh.gov

National Institutes of Health: Funding Opportunities and Notices Database
http://grants.nih.gov/grants/guide/index.html

National Science Foundation: Index of Funding Opportunities
http://nsf.gov/funding

Grants.gov - federal clearinghouse and application portal
www.grants.gov