Masters of Photography: An excellent link for photographic images from the dawn of the medium until now. Arranged by artist.
Prints and Photographs Division: Advertising and Propaganda, American Memory Project, Library of Congress which comprise an estimated 13.7 million items.
Robert Mapplethorpe Foundation: Source for biography and selections from the portfolio of this American photographer’s work.
Sandy Skoglund Studio: The official site with source information, images and installation works categorized by date. An important American photographer and installation artist.