AP Photo Archive - Includes press photographs and audio dating back to 1826.[UW restricted]
American Memory - Historical documents, photographs, sound recordings, moving pictures, books, pamphlets, maps, and other resources from the Library of Congress.
LIFE photo archive - Millions of photographs from the LIFE photo archive, stretching from the 1750s to today. Most were never published and are now available for the first time through the joint work of LIFE and Google.
New York Public Library Digital Galleries - Source for historical images, maps and documents.
Digital History: American Historical Images - an online collection of historical images hosted by the University of Houston in partnership with other institutions. The images are categorized in over 20 categories from advertisements to daguerreotypes to political history and more.
Here are some examples of Digital Archives and Collections that you may want to look at:
African American history
African American Studies Center The Oxford African American Studies Center provides more than 10,000 articles by top scholars in the field. The core content includes:
John Henrik Clarke Africana Library (Cornell) full-text digital historical texts