Executive

Office of Management and Budget
The White House

Congress

Library of Congress
U.S. House Of Representatives
U.S. Senate

Agencies

Center for Disease Control - CDC
Congressionally Directed Medical Research Programs - CDMRP
Center for Disease Control - CDC
Cooperative State Research, Education, and Extension Service - AGRIC CSREES
Environmental Protection Agency - EPA
Federal Demonstration Partnership - FDP
Fullbright Programs
Internal Revenue Service - IRS
National Aeronautics and Space Administration - NASA
National Endowment for the Arts - NEA
National Endowment for the Humanities - NEH
National Institutes of Health - NIH
National Science Foundation - NSF
U.S. Patent and Trademark Office

Departments

U.S. Department of Agriculture - AGRIC
U.S. Department of Commerce - COMM
U.S. Department of Defense - DOD
U.S. Department of Education - DED
U.S. Department of Energy - DOE
U.S. Department of Housing and Urban Development - HUD
U.S. Department of Interior - INTER
U.S. Department of Justice - JUSTC
U.S. Department of Labor - LABOR
U.S. Department of State - STATE
U.S. Department of Transportation - TRANS

Comprehensive

Grants.gov
Federal Agency Directory (from LSU)
FedWorld
FirstGov
infoUSA (International Programs Information)
Office of the Federal Register