There are many free and commercial Internet sources of georeferenced satellite imagery and aerial photography usable in GIS programs. Most state governments in the United States archive imagery on GIS clearinghouse Web sites providing downloadable data without charge to users. Internet searches for either satellite imagery or aerial photography associated with a state or locality will yield Web addresses for available imagery. Larger localities may have a GIS coordinator who can provide the information for you. Otherwise, contact the local planning department or the engineering department directly. You can also contact your state GIS coordinator or council for additional information. A list of state GIS contacts is available through the National States Geographic Information Council (NSGIC).
The U.S. Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) archives aerial and satellite imagery for all areas of the United States and much of the world. TerraLook, an EROS imaging and downloading tool, is a source of USGS-archived satellite imagery for any location on Earth. This site requires registration, but there is no charge for the data.
The United States Department of Agriculture (USDA) and Natural Resources Conservation Service (NRCS) operate the Geospatial Data Gateway which houses a wide variety of GIS data intended for use in agricultural and natural resource management. This Web site includes free access to the 1-meter resolution color National Agricultural Imagery Program (NAIP) aerial photography available by year for United States counties.
The Digital Northern Great Plains Web site archives free, downloadable satellite imagery for Idaho, Montana, Wyoming, Minnesota, and North and South Dakota.
AmericaView members provide access to satellite remote sensing data (usually LandSat or MODIS). Refer to the AmericaView State Membership Directory for contact information in your state.
The Global Land Cover Facility at the University of Maryland also provides a wide selection of satellite imagery and derived products for the United States and other parts of the world.