History

George Eastman House Collections
Collection includes thousands of photographs and negatives dating from the invention of photography to the present day including many milestones and covering most photographic processes.
http://www.eastmanhouse.org/inc/collections/photography.php

A History of Photography
Contains an extensive history, from earliest times to the 1920s. Includes biographical information on all significant photographers.
http://www.rleggat.com/photohistory/

History of Photography Timeline
Highlights major developments in timeline format.
http://photo.net/learn/history/timeline

The Keystone-Mast Collection
Archive at the California Museum of Photography offers an encyclopedic view of world history and cultural diversity.
http://www.cmp.ucr.edu/mainFrame/collections/guides/kmast/