Geocoding Web Services

GeoNames

 * 1) extensive array of available services
 * 2) extensive reverse geocoding & proximity services
 * 3) findNearbyPlaceName
 * 4) findNearbyStreets & findNearbyIntersection (TIGER & OSM)
 * 5) findNearbyAddress
 * 6) findNearbyWikipedia

Google

 * 1) requires Google API key
 * 2) limited to license agreement (site must be external & requests limited)
 * 3) traditional and reverse geocoding services