The GeoNames geographical database covers all countries and contains over eleven million placenames that are available for download free of charge.
Web services data API: http://www.geonames.org/export/ws-overview.html
Poke around in there, you'll find some interesting things, like earthquakes, geolocated datasets (eg, nearby Wikipedia pages), Open Streetmap interface. They might even be useful.
A free, publically referrable, publically editable street map of the world, generated out of data contributed by the people who live there.
A collaborative website which maps wireless access points all across the world using information donated by enterprising wardrivers.
4481 links, including 318 private