Flickr seems to be being used more and more as a place to upload historical images, especially in America. The Library of Congress is a good source and recently posted some rare photos of Lincoln to celebrate President's Day. Check out the section News in the 1910s for some great photos of America and world in the early 20th century.
(Image from the Bain News Service 1910-1915 - Colliery Lasses, British Coal strike)
