US Geological Survey Images

This site has a collection of public domain images taken by the US Geological Survey from 1872-1991. There are a lot of really amazing images of the great quake of 1906 and many other items of interest to be found.

http://www.gliff.org/usgs/

Found on the ever brilliant BoingBoing, one of whose contributors, Mark F. if a Uke fan who also runs the also excellent Ukulelia.