Magnum Photos

Here is a website that may be of interest to you. Here is a description from the homepage.

Magnum Photos is a photographic cooperative of great diversity and distinction owned by its photographer members. With powerful individual vision, Magnum photographers chronicle the world and interpret its peoples, events, issues and personalities.
The Magnum Photos library is a living archive updated daily with new work from across the globe. You may search or browse our 400,000+ images which are available online for licensing in a variety of formats.

http://www.magnumphotos.com/Archive/C.aspx?VP=XSpecific_MAG.AgencyHome_VPage&pid=2K7O3R1VX08V