The Commons is an amazing part of Flickr which shares public domain photographs (from up to 120 years ago) archived by museums and libraries. Their goal is to simply have users tag the photos in order to keep the archives organized.

While on the subject of public domain, check out archive.org. Here you will find tons of texts, movies, and audio files that are open for anyone to download.

The picture above is around 100 years old and is part of the Lantern Slide Collection from the Brooklyn Museum. Also check out these two ladies boxing,