The following sites have digital photographs or images related to the geological sciences that can be used for educational purposes:
Earth Science World Image Bank - a collection of photographs and images on a wide variety of earth science topics provided by the American Geological Institute (AGI). The Image Bank makes quality geoscience images available to the public, educators, and the earth science community.
USGS Earth Science Photographic Library - the U.S. Geological Survey has a collection of over 400,000 taken in the process of doing geologic research in the United States and U.S. territories from 1868 to the present. These images document the discovery, development, and science in the U.S. done by the Geological Survey and its predecessors. This site provides online access to some of these photographs.
BLM Image Library - a photographic library of digital images taken by BLM employees in areas managed by the Bureau of Land Management.
NASA Image Exchange (NIX) - a search engine that can look for photographs and images on a wide variety of topics at all NASA sites. Most photographs are digital and can be viewed online.
ClipArt Etc. Earth Science - this site, which is produced by the Florida Center for Instructional Technology, is a clearinghouse for clip art and images related to Earth Science. It includes images of minerals, geologic structures and fossils.