Geocoding is the process of turning a text form location (such as an address or name of a place) into a set of geographical coordinates. The inverse, reverse geocoding, turns a set of geographical coordinates into an address or a place name. Either method, or both, might be used for location aware applications, or during the process of computing locations for checkins.
- Aaron Parecki geotags all his posts to display the city name of where the post was created. The geocoding is done via Atlas
- Nominatim uses OpenStreetMap data
- Google Maps Geocoding API
- Geocoder (U.S. Census Bureau)
- Esri's mapping services
- http://www.geonames.org/ - not strictly a geocoding service, but has free databases/webservices for countries, postal codes, placenames, and their coordinates.
- https://getlon.lat/ nice overview of (reverse) geocoding service options