DTED0

Coverage	Web link
Worldwide elevation	http://geoengine.nima.mil/muse-cgi-bin/rast_roam.cgi

ESRI shape

Coverage	Web link	Alternative web link
Worldwide map of countries	http://en.wikipedia.org/wiki/Global_Administrative_Unit_Layers_(GAUL)	http://www.bluemarblegeo.com/products/worldmapdata.php?op=download (a lower resolution map)
US time zones	http://www.nationalatlas.gov/mld/timeznp.html	0
US states	http://www.nationalatlas.gov/mld/statesp.html	http://www.census.gov/geo/www/cob/st2000.html#shp
US counties	http://www.nationalatlas.gov/mld/countyp.html
US ZIP codes	http://www.census.gov/geo/www/cob/z32000.html for 3 digits	http://www.census.gov/geo/www/cob/z52000.html for 5 digits

ESRI shape or TIGER/Line

Coverage	Web link
USA	http://www.census.gov/geo/www/tiger/

GeoTIFF, JPG or PNG

Coverage	Web link
Worldwide	http://www.unearthedoutdoors.net/global_data/true_marble/download
Worldwide satellite map from NASA	http://earthobservatory.nasa.gov/Features/BlueMarble/ with a download mirror at http://mirrors.arsc.edu/nasa/world_500m/	http://neo.sci.gsfc.nasa.gov/Search.html (a lower resolution map)

GTOPO30

Coverage	Web link
Worldwide elevation	http://edc.usgs.gov/products/elevation/gtopo30/gtopo30.html