Guide to Geographic Information Systems GIS Dictionary Index of GIS Net Sites Planetary GIS Map Maker National Geographic MapMachine National Atlas National Atlas Map Maker Nation's Topography Map for 21st Century FEMA Maps United States Census Maps American FactFinder Data Sets Federal Government GIS Data Sources ESRI GIS and Mapping Software Virginia Economic Development Partnership Roanoke Virginia GIS Site National Renewable Energy Lab Maps and GIS Data Globe Explorer--instant satellite photos Center for Geographic Information Sciences University of Virginia Data Center James Madison University Spatial Information Clearinghouse Chesapeake Bay Information Science for a Changing World