The following research libraries have notable digital collections and this list is a sampling of resources available. In most cases, the digitized items available represent only a small fraction of the library's holdings.
American Museum of Natural History - Anthropology: "Over 250,000 ethnographic and archaeological objects representing the peoples of the Americas, Africa, Asia, Europe and the Pacific Islands have been digitally imaged and are accessible online."
American Museum of Natural History - Virtual Library: Includes AMHN Scientific Publications, digitized scientific manuscripts and field notes, and other popular publications.
Archives of American Art: "a virtual repository of a substantial cross-section of the Archives' most significant collections. Since 2005, over 240 archival collections have been digitized and posted online comprising 2.9 million images. In addition, nearly 18,000 documents have been individually cataloged and are accessible through the Search and Browse interface."
Harvard Digital Collections: "Provides free, public access to more than 6 million objects digitized from our collections - from ancient art to modern manuscripts and audio visual materials."
Ransom Center Digital Collections: "These collections represent just a sample of the Ransom Center's diverse holdings in literature, photography, film, art, and the performing arts." It includes over 90 collections.
Smithsonian Libraries - Digital Library: "Includes over seven thousand rare books, journals and manuscripts online ranging from advertising and aeronautics to zinc sculpture and Zuni cuisine, though the focus is on the broad topics of History and Culture, Art and Design, and Science and Technology."
Tulane University Digital Library "Rare and unique collections in the areas such as Latin American Studies, jazz, New Orleans and Louisiana History and architecture..."
University of Washington Digital Collections: "Features materials such as photographs, maps, newspapers, posters, reports and other media from the University of Washington Libraries (including Special Collections), University of Washington Faculty and Departments, and organizations that have participated in partner projects with the UW Libraries. The collections emphasize rare and unique materials."
Umbra Search African American History: "Brings together hundreds of thousands digitized materials from over 1,000 libraries and archives across the country [to] makes African American history more broadly accessible."
GA State Archive
Remember: you can always use Google to locate the website for a country's national library or national archives.
Endangered Archives Programme - British Library: "The Endangered Archives Programme facilitates the digitisation of archives around the world that are in danger of destruction, neglect or physical deterioration. ... Since 2004, the [EAP] has digitised over 7 million images and 25 thousand sound tracks. Archive types digitised ... include rare printed sources, manuscripts, visual materials, audio recordings."