Magnum
Founded in 1947, Magnum is a cooperative of nearly 60 photographers. Magnum members include legends like Robert Capa and Henri Cartier-Bresson and great contemporaries including David Alan Harvey and Steve McCurry. The site provides biographies and photo galleries of each of its members.
VII
Named after the number of its founding members, the VII site showcases some of the best international photojournalism. The agency's members have covered nearly every conflict in recent memory, collecting awards along the way. Visitors can view hundreds of photographs organized into beautiful galleries.
Black Star
An agency that traces its roots to the 1930s, Black Star shares a history with LIFE magazine. The agency has been an incubator for the world's best photojournalists, evidenced by several photographers that went on to join Magnum and VII. The site offers small mosaics of photographs from each decade of its existence, but they are not as engaging as the galleries of Magnum and VII.
Washington Post
Washington Post photographers have more combined Pulitzers than any other photography department in the country. The site has biographies and galleries of Pulitzer winners Carol Guzy, Michael Williamson, Lucian Perkins and other great staff photographers. This news-intensive site offers other photo features including "The Day in Photos," "Top Story" and "The Week in Review."