"GeoNames is a free and open source geographical database.
Primarily for developers wanting to integrate the project into web
services and applications, it integrates world-wide geographical
data including names of places in various languages, elevation,
population, and all latitude / longitude coordinates. Users are
able to manually edit, correct and add new names with a
user-friendly wiki interface. The data is accessible through a
number of webservices and a daily database export.
"Launched at the end of 2005, GeoNames is already serving up to
over 3 million web service requests per day, and contains over
eight million geographical names..."