Open Source Data Resources
Open Street Map (global coverage of baseline datasets)
This download site offers a database dump of the OpenStreetMap Full Planet in OSM XML file format and Protocolbuffer Binary Format. Also available are extracts of more than 200 cities and regions world wide in different formats
Digital Elevation Model
Digital elevation data at 90m resolution. The Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA) jointly announced the release of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model Version 2 (GDEM V2) on October 17, 2011
United Nations Environment Programme' Environmental Data Explorer
Provides baseline data such as landuse, administrative boundaries, social economic, and population.
NASA Earth Observations (NEO)
European Space Agency (ESA)
DIVA-GIS provides free spatial data for the whole world.