There's a lot GIS data available out there, but where exactly is it and how can you find it? The list below will help to get you started.
- http://www.esri.com/data/find-data.html: With ArcGIS you get large amounts of up-to-date, ready-to-use content covering the entire world. This content comes from commercial providers and the GIS community.
- http://www.data.gov/home: High value datasets generated by the Executive Branch of the Federal Government.
Geospatial Data Gateway (GDG)
- http://datagateway.nrcs.usda.gov/: One-stop-source for environmental and natural resources data anytime, from anywhere, to anyone. Includes many links to other GIS data sites.
USGS – The National Map
- http://nationalmap.gov/: Current US topo map layers are in http://nationalmap.gov/ustopo/index.html. Orthoimage base, transportation, geographic names, topographic contours, boundaries, hydrography, woodlands, the Public Land Survey System (PLSS) and the US National Grid (USNG).
USGS – National Hydrography Dataset (NHD)
- http://nhd.usgs.gov/data.html: Vector dataset containing features such as lakes, ponds, streams, rivers, canals, dams and stream gages. For use in general mapping and analysis of surface water systems.
USGS – National Map Viewer
- http://viewer.nationalmap.gov/viewer/: Visualize, inspect download current topographic base map data and products for free.
US Census Bureau
- http://www.census.gov/: Online interactive maps, tools and products to display and work with demographic data.
- http://archive.org/details/maps_usgs: Download USGS DRG maps of the 50 states; Includes many links to other related sites.
GIS Data Depot
- http://data.geocomm.com/: Users should be GIS-proficient and may require access to GIS software; Includes some international data and US State data bundles on CD-ROM, for a fee.
- http://www.terraserver.com/view.asp: Online satellite imagery downloads in a variety of pixel sizes, for an additional fee can include a georeferenced worldfile with metadata.