Geonames is a geographical database with web services that let users extract useful information about different places, such as weather, timezone and post codes. The GeoNames geographical database covers all countries and contains over eight million placenames that are available for download free of charge. Users can edit, correct and add new names using a wiki interface.
Geonames provides a suite of Webservices including the following categories:
The APIs use RESTful protocol and responses vary in format between XML, JSON, CSV, and TXT
While the GeoNames data is free, the data is available without costs, there is a Service Level Agreement available for premium web services.