Yahoo! PlaceFinder

Yahoo! PlaceFinder is a geocoding Web service that helps developers make their applications location-aware by converting street addresses or place names into geographic coordinates (and vice versa). PlaceFinder recognizes a large number of place formats and returns rich geographic data about each result, including geographic coordinates, address components, and WOEID. The WOEIDs returned by the service can be passed to Yahoo!'s GeoPlanet API for further geographic enrichment and discovery. PlaceFinder replaces the Yahoo! Maps Web Services Geocoding API, which has been deprecated.
More information: http://developer.yahoo.com/geo/placefinder/