Last week Google announced the availability of about 2 million images from LIFE magazine’s archives, many of them never published before now. Over the next few months, the entire archive of about 10 million images should be available through Google’s image search. To see the images, you can either go to the collection’s main page or do a regular Google image search, but specify that you want to search within the LIFE collection by adding “source:life” to your search string (example: “Dorothea Lange soure:life”). The images come with some descriptive information, and you can access a decent-sized jpeg image (1280 pixels on the long side), but note that they neither prohibit nor permit use of the images in a context other than Google Image Search.
(results from a search on Matisse)
What can be better than that? The U.S. Geological Survey’s Photographic Library doesn’t rival the LIFE archive’s size or scope, but the quality is phenomenal and the images are all in the public domain (which means you can use them as you wish, as long as you cite the photographer — more information here). You’ll find some great examples of early photography on this site, including images by W.H. Jackson, John Hillers, and others. Also, there’s good coverage of some ancient monuments like Mesa Verde. The images are positively huge, free to use, and are accompanied by good descriptive information.
(An image of Hovenweep National Monument by W.H. Jackson, 1874. Full record here)