GeoNames is YAG (yet another geocoder), but behind the curtains lie many cool features. The most unique of which is a reverse geocoder.

Reverse geocoding is converting Latitude & Longitude to a place name. This is the other side of the mirror from traditional geocoding, which converts a place name into latitude & longitude. Why would someone want to reverse geocode you ask? With reverse geocoding you can convert your GPS tracklogs into meaningful locations easily, or allow users to click on a map and get back actual location of where they’re clicking.

The GeoNames API provides an interface for getting nearby postal codes, country, or most specific: place names.

Example

HighEarthOrbit offices: http://ws.geonames.org/findNearbyPlaceName?lat=42.4266&lng=-83.4931&style=full

returns:

<geonames>
  <geoname>
    <name>Northville</name>
    <lat>42.43111</lat>
    <lng>-83.48333</lng>
    <geonameid>5003956</geonameid>
    <countrycode>US</countrycode>
    <countryname>United States</countryname>
    <fcl>P</fcl>
    <fcode>PPL</fcode>
    <fclname>city, village,...</fclname>
    <fcodename>populated place</fcodename>
    <population>6360</population>
    <elevation>252</elevation>
    <admincode1>MI</admincode1>
    <adminname1>Michigan</adminname1>
    <admincode2 />
    <adminname2 />
  </geoname>
</geonames>

The whole geo-enchilada

Lastly, to make you really feel warm and good inside, the GeoNames database is provided for direct download under a Creative Commons Attribution license. Yum, free data.

See the GeoNames Blog post about it.