The Sect of Rama

Via boingboing, someone has put together an indexed site of 120 years of United States Geological Survey images, all in the public domain.

I suggest going through them chronologically. Some really sweet shots of San Francisco post 1906 earthquake, a lull during WWII (after which the shots are mostly color), all the way to more recent events, such as the 1989 quake. Not all images are from the US, and there are some pretty dull categories like erosion and minerals, but still worth poking around for the plentiful gems (ok, thats a bad pun).