There are a number of types of data resources available for geospatial technologies. There is free downloadable GIS files, connections to data servers; connections to image servers. Data can also be purchased from industry leaders and other vendors. The sources of data can range from local; state; regional; national and international data.

Downloadable GIS files & Connection Servers

National Atlas
(http://nationalatlas.gov/)

National Map
(http://nationalmap.gov/)

GeoData.gov
(http://gos2.geodata.gov/wps/portal/gos)

National Park Service GIS Resources
(http://www.nps.gov/gis/)

USDA Natural Resources Conservation Service (http://www.nrcs.usda.gov/technical/maps.html)

National Hydrography Data Set
(http://nhd.usgs.gov)

USGS Geographic Data Center Download Site
(http://edc2.usgs.gov/geodata/index.php)

ArcGIS Resource Center (Desktop)
(http://resources.esri.com/arcgisdesktop/index.cfm?fa=content)

ArcGIS Resource Center (ArcExplorer)
(http://resources.esri.com/arcgisexplorer/index.cfm?fa=content )

ArcGIS Resource Center (ArcGIS Online)
(http://resources.esri.com/arcgisonlineservices/index.cfm?fa=content)

GIS Data Depot
(http://www.gisdatadepot.com)