Google Maps: providing topographic maps and satellite imagery for much of the world--see Google.
EROS Data Center of the U.S. Geological Survey. Primary site for all digital datasets of the United States including maps, satellite imagery, digital elevation, airphotos, and much more. Go to EDC.
TopoZone: providing free USGS topographic maps of the entire United States at all sizes and scales--see TopoZone.
GeoCommunity: portal and clearinghouse for GIS datasets, software, careers, and more. A good source for downloading GIS datasets. Go to GeoCommunity.
Association for Geographic Information, dictionary of GIS terminology and acronyms--see AGI-GIS.
AmericaView, a national consortium for remote sensing education, research, and geospatial applications. Go to AmericaView.
Earth and Moon viewer that includes topographic maps, satellite images, and composite views at different scales and vantage points--see Earth views.
Detailed highway and street maps of the contiguous United States--see Maps On Us.
U.S. Geological Survey, national mapping information--see USGS mapping.
Earthshots: Satellite images of environmental change. U.S. Geological Survey, EROS Data Center--see Earthshots.
Introduction to geographic information systems, U.S. Geological Survey--see GIS.
Animated map showing evolution of boundaries for the contiguous United States--see U.S. boundaries.
National Imagery and Mapping Agency (formerly Defense Mapping Agency)--see NIMA.
National Biological Information Infrastructure, Bird Conservation Node interactive map of North America.
Interactive map of North American mammals from the Smithsonian National Museum of Natural History.
World Wildlife Fund WildFinder: Mapping the world's species.
Selected state GSA resources
KansasGIS: Web-based interactive maps and GIS datasets for the state of Kansas--see KansasGIS.
KansasView: A consortium of universities and governmental agencies working cooperatively to advance the use of remote sensing and GIS technologies--see KansasView.
Digital atlas of Montana, an interactive map builder--see Montana mapper.
New Mexico Resource Geographic Information System, a cooperative program between the University of New Mexico and the State of New Mexico Information Technology Commission--see New Mexico RGIS.
University of Texas Libraries, Perry-Castaņeda Library Map Collection. Among of the best map libraries in the United States. Go to UT maps.
Interactive state and county maps from Texas A&M University. Go to TAMU maps.
Interactive California Environmental Management, Assessment, and Planning System. Web-based interactive natural-resources query GIS for the state of California--see ICE Maps 2.
Interactive map of Oklahoma wildlife management areas.
Florida Natural Areas Inventory (works only with Internet Explorer).
Specific GSA software
Idrisi from Clark University, Massachusetts. The most widely licensed raster-based GIS software in the world. It combines ease of use and low cost with surprisingly powerful analytical and image-processing capabilities. Go to Idrisi.
ESRI is the commercial source for the ArcGIS suite, the most widely used vector-based GIS software in the world. Go to ESRI.
Global Mapper and GIS viewer capable of displaying the most popular raster, elevation, and vector datasets. Originally developed by the USGS, it can import and export GIS datasets in many common formats. A free trial version is available--see Global Mapper.
MICRODEM is freeware for use with digital elevation models, satellite imagery, and other GIS datasets. Developed by Prof. Guth of the U.S. Naval Academy--see MICRODEM.
U.S. and international GSA resources