From the American Geological Institute, the Image Bank provides quality geoscience/earth science images.  The archive may be browsed by categories, or searched by key word or location.  Most imagery is available online at a higher-resolution suitable for on-screen display.  All images are available at no cost for non-commercial use.

Collections of photographs and other images available for use by the public.

The National Biological Information Infrastructure's Digital Image Library contains a wide variety of images related to nature and the environment.  Topics include bodies of water, environmental issues, habitats/landscapes, management, plants and animals.