GIScience, Institute of Geography, University of Heidelberg
OSGeo: The Open Source Geospatial Foundation
OpenNauticalChart: Free nautical chart
OpenSeaMap: Free nautical chart
OpenTerrain: The main topic of this site is the visualization of
geospatial and medical data with open-source software.
OpenTopography facilitates community access to high-resolution, Earth science-oriented, topography data, and related tools and resources.
NASAs WorldWind: Open Source Globe Viewer