Natural Earth – world maps – Excellent world shapefile maps with national boundaries, first order admin (provinces, states, etc.), disputed areas, coastlines, populated areas and more at various scale levels.
United Nations – UN-SALB (Second Administrative Level Boundaries) data set project. These maps are free but copyright rests with the UN. The maps are validated by the National Mapping Agencies (NMA) of each UN Member State. This website requires registration to download the maps.
DIVA-GIS – Free country level maps, including administrative boundaries, roads, railroads, altitude and land cover.
Geocommons – A huge database of user submitted maps. Search for any kind of map, then click on the “shapefile” button to the right of the map (if available) to download the shapefiles.
World Bank – Country shapefiles can be downloaded through the World Bank’s Mapping platform as follows: Click on ‘explore countries’ to select a country, click on ‘download’ in the top-right corner, and select ‘Indicators (shapefile)’. This option is not available for all countries.
Map Library – Country shapefile maps for Africa in the public domain.
MapCruzin – A great source for all kinds of shapefiles.
Open Street Map – A growing collection of shapefile map downloads by continent, region and country. These maps are community edited and are not always complete. Shapefiles by country are also available from VDS tech.