Shorpy.com is a great photo site for history buffs.  The site collects photos from the Library of Congress’ archive, processes them for contrast and posts them in high resolution. Some are over 2000 pixel along the long edge which allows you to clearly see details in the photos and really get immersed in what’s going on.
Most are from 1910 – 1930, but there are some excellent color photographs of the World War II era as well.
