• Internet Archive
• National Archives
• Library of Congress – Digital Collections
• Smithsonian – Open Access
• NASA Image and Video Library
• U.S. Fish and Wildlife Service- National Digital Library
• U.S. Geological Survey – Library Photographic Collection
• Open Library
• Digital Public Library of America
• Project Gutenberg
• Europeana
• HathiTrust Digital Library
• Biodiversity Heritage Library
• The Public Domain Review