I love old photographs - especially good ones. And whether you're digging into your family's history, curious about your hometown, or just want to escape (temporarily) into a world before BSODs, DDR3 DRAM, and the nVidia-ATI-Intel war, Flickr's The Commons is a great place to spend some time.
The Commons is an online collection of copyright-free photos from a variety of institutions, including the Brooklyn Museum, the Library of Congress, the Powerhouse Museum, and now the Smithsonian Institution . The Microsoft Pro Photo Blog reports that eventually 2000 photos will find their way from the Smithsonian's collection to Flickr.
Follow these links to the following photostreams on Flickr:
...OK, you caught me: my photos are not historically significant - yet. Come back in 30 or 40 years and we'll talk about it.