GIS/GPS Companies and Firms:

• ESRI
• Garmin
• U.S. Dept of the Interior
  • U.S. Geological Survey
• Google (for Google Earth)
• Geospatial Technologies, Inc.

Non-Profit Organizations and Independent/Public Projects

• The GIS Data Depot
• Open GIS Consortium, Inc.
• GeoCommunity
• GRASS GIS
• The Free GIS Project