Sirs Researcher (Proquest)

A library subscription database that provides photos, charts, graphs, and other images for a wide variety of topics.

 Academic Search Complete (EBSCO)

Academic Search Complete provides a database of graphics and photos in the following categories: Flags, historical photos, photos of places and people, natural science photos and maps.

 Google Image Search

More than 880 million images are indexed and searchable through the popular Google search interface.

 New York Public Library Digital Gallery

According to the site, The NYPL Digital Gallery "provides access to over 275,000 images digitized from primary sources and printed rarities in the collections of The New York Public Library, including illuminated manuscripts, historical maps, vintage posters, rare prints and photographs, illustrated books, printed ephemera, and more."

 Photovault

Provides access to thousands of photos organized through a category structure. Categories range from Aerospace to Universe. There is also a keyword search engine.

 Digital Librarian: Images

One librarian's extensive directory listing of web sites featuring various images and image collections.

 Free Graphics

According to this site, it features "the Internet's top 496 free graphics links". Includes links to sites featuring clip art, wallpaper, backgrounds, web graphics and photos.

 New York Public Library Picture Collection Online

According to the site, this is "a collection of 30,000 digitized images from books, magazines and newspapers as well as original photographs, prints and postcards, mostly created before 1923."

 American Memory - The Library of Congress

American Memory provides free and open access to written and spoken words, sound recordings, still and moving images, prints, maps, and sheet music that document the American experience.

 Smithsonian Photography Initiative

This site provides online photography from the Smithsonian Institution's 18 museums and galleries, 9 research centers, and the National Zoo. The collections represent more than 100 photographers, using over 50 different photographic and image-making processes.