The Library of Congress Flickr account photostream page one is thing of beauty right now. They feature a handfull of brick buildings from the American mid-west.
Just look at the color of this sky:
More: the Internet Archives is re-opening the Public Domain, which they’re billing as a chance to celebrate the Public Domain. It’s a great chance to teach students about it, I spent an hour or so this past week showing my students about various PD media, and it was well worth it.