Environmental System Research Institute (ESRI) Official Homepage: Home of ArcGIS, with user support, downloads, and tutorials for the range of GIS products, including ArcView, ArcGlobe, and ArcGIS extensions.

GIS.com: Useful information on the uses of GIS, implementation, careers, and other information for beginners.

GIS Lounge: GIS user community with helpful information, downloads, and other resources for beginners and advanced users.

GIS Development: Geospatial resource portal offering with news, downloads, tutorials, publications, and other information.

Institute for Geographic Information Science: Offers support, forums, training, and other GIS-related services

ITT Visual Information Solutions: Source for GIS, ENVI, and other geospatial imagery.

Colleges/Universities

Center for Spatially Integrated Social Science: Links, tutorials, and resources for GIS-based research in the Social Sciences. Maintained by the University of California-Santa Barbara.

University Consortium for Geographic Information Science

Vanderbilt University Library: