the flickr commons
If you haven’t, go check out the Flickr Commons. “The key goals of The Commons on Flickr are to firstly show you hidden treasures in the world’s public photography archives, and secondly to show how your input and knowledge can help make these collections even richer.” And if you’re not the tagging or commenting type, browsing works, too because every once in a while you come across gems like this one from the collection of the State Library of New South Wales. (Baldessari, anyone?)