GeoNames
GeoNames is a geographical database available and accessible through various web services, under a Creative Commons attribution license.
Database and web services
The GeoNames database contains over 10,000,000 geographical names corresponding to over 7,500,000 unique features. All features are categorized into one of nine feature classes and further subcategorized into one of 645 feature codes. Beyond names of places in various languages, data stored include latitude, longitude, elevation, population, administrative subdivision and postal codes. All coordinates use the World Geodetic System 1984 (WGS84).
Those data are accessible free of charge through a number of Web services and a daily database export.
Wiki interface
The core of GeoNames database is provided by official public sources, the quality of which may vary. Through a wiki interface, users are invited to manually edit and improve the database by adding or correcting names, move existing features, add new features, etc.
Semantic Web integration