I found a online free GeoNames lookup service

main page:
http://www.geonames.org/

the api overview:
http://www.geonames.org/export/ws-overview.html

api templte:
http://api.geonames.org/method?params=query&username=yourname

the jeoquery.js file for jquery using
http://tompi.github.io/jeoquery/jeoquery.js

var methods = {
astergdem: {params: ['lat', 'lng'] },
children: {params: ['geonameId', 'maxRows'] },
cities: {params: ['north', 'south', 'east', 'west', 'lang'] },
countryCode: {params: ['lat', 'lng', 'type', 'lang', 'radius'] },
countryInfo: {params: ['country', 'lang'] },
countrySubdivision: {params: ['lat', 'lng', 'level', 'lang', 'radius'] },
earthquakes: {params: ['north', 'south', 'east', 'west', 'date', 'maxRows', 'minMagnitude'] },
findNearby: {params: ['lat', 'lng', 'featureClass', 'featureCode', 'radius', 'style', 'maxRows'] },
findNearbyPlacename: {params: ['lat', 'lng', 'radius', 'style'] },
findNearbyPostalCodes: {params: ['lat', 'lng', 'radius', 'style', 'maxRows', 'country', 'localCountry', 'postalCode'] },
findNearbyStreets: {params: ['lat', 'lng', 'radius', 'maxRows'] },
findNearbyStreetsOSM: {params: ['lat', 'lng'] },
findNearbyWeather: {params: ['lat', 'lng'] },
findNearbyWikipedia: {params: ['lat', 'lng', 'radius', 'maxRows', 'country', 'postalCode'] },
findNearestAddress: {params: ['lat', 'lng'] },
findNearestIntersection: {params: ['lat', 'lng'] },
findNearestIntersectionOSM: {params: ['lat', 'lng', 'radius', 'maxRows'] },
findNearbyPOIsOSM: {params: ['lat', 'lng'] },
get: {params: ['geonameId', 'lang', 'style'] },
gtopo30: {params: ['lat', 'lng'] },
hierarchy: {params: ['geonameId'] },
neighbourhood: {params: ['lat', 'lng'] },
neighbours: {params: ['geonameId', 'country'] },
ocean: {params: ['lat', 'lng', 'radius'] },
postalCodeCountryInfo: {params: [] },
postalCodeLookup: {params: ['postalcode', 'country', 'maxRows', 'charset'] },
postalCodeSearch: {params: ['postalcode', 'postalcode_startsWith', 'placename_startsWith', 'country', 'countryBias', 'maxRows', 'style', 'operator', 'charset', 'isReduced'] },
search: {params: [ 'q', 'name', 'name_equals', 'name_startsWith', 'maxRows', 'startRow', 'country', 'countryBias', 'continentCode', 'adminCode1', 'adminCode2', 'adminCode3', 'featureClass', 'featureCode', 'lang', 'type', 'style', 'isNameRequired', 'tag', 'operator', 'charset', 'fuzzy'] },
siblings: {params: ['geonameId'] },
srtm3: {params: ['lat', 'lng'] },
timezone: {params: ['lat', 'lng', 'radius', 'date'] },
weather: {params: ['north', 'south', 'east', 'west', 'maxRows'] },
weatherIcao: {params: ['ICAO'] },
wikipediaBoundingBox: {params: ['north', 'south', 'east', 'west', 'lang', 'maxRows'] },
wikipediaSearch: {params: ['q', 'title', 'lang', 'maxRows'] }
};

using example:
http://api.geonames.org/children?geonameId=3175395&username=demo
http://api.geonames.org/countryInfo?country=TW&username=demo