The source of a tremendous amount of public domain works.
By law, works by an employee of the US government are not covered by US copyright law (source).
- CIA World Factbook ● Details about all the countries of the world.
- NASA ● You've probably heard of it.
- NASA Images ● A collection of photographs from NASA.
- The Best Copyright-Free Photo Libraries ● A collection of US Government photo libraries.
- White House ● The website of the President of the United States.