jQuery Geo is a plugin for the popular framework that provides an easy-to-use API for map/geolocation related actions.

The plugin uses the open source map servers like Open Street Map, WMS and Esri ArcGIS (Open Street Map by default) for pulling the map data and can:

• show mapping data and handle direct user interaction with the map
• use geospatial functions like calculating bounding boxes, measuring the distance between geometries, etc.

The maps created are mobile-friendly and have lots of built-in methods for customization.

jQuery Geo is very well-documented and supported with a bunch of examples.

SimpleGeo is a free service which makes creating location-aware applications so simple.

A powerful API & SDKs for various languages exist to easily communicate with the service.

It has 2 free services:

SimpleGeo Context

Using SimpleGeo Context, you can get many details by providing a latitude/longitude like the name of the location, its weather, geographic features, etc.

SimpleGeo Places

It is the world's first open POI (point of interest) data which is maintained by SimpleGeo to make sure it is accurate.

Using SimpleGeo Places, it is possible to learn shopping centers, gas stations, movie theaters, etc. around any given location.

Both services are 100% free with no usage limits.

MooGeo is a MooTools plugin that makes accomplishing common geolocation tasks easy.

These tasks include getting detailed info about an IP (country, city, longitude, latitude, etc.), parsing geographical data from text and even finding Flickr photos about a given place.

The plugin makes use of multiple free-to-use services like:

• Yahoo PlaceMaker
• Yahoo GeoPlanet
• jsonip.appspot.com
• W3C Geo location
• Flickr.places.findLatLon

and wraps them into a single package.

MooGeo has also support for events on every level (when a request is sent, completed, success or error) which helps offering a better experience to end users.

GeoNames is a set of  free and downloadable geographical databases of all countries which includes over 8 million place names.

The data comes in tab-delimited + utf-8 formatted text files and can be downloaded as a whole or per country.

Besides the locations of the places/cities/countries, databases include supplementary data like capitals, statistics, timezones and more.

GeoNames data can also be reached from their free webservice which can return results in XML and JSON.

Geolocation is one of the most popular subjects for today's web & there are many solutions that help geo-enabling web applications.

YQL Geo Library is an impressive resource for geolocation as it is totally free & JavaScript-based.

It has various powerful features like:

• detecting the visitor’s location with the W3C geo API and with IP as a fallback
• find geo location from text
• find location from lat/lon pair
• find locations in a certain web document (by URL)
• get the location for a certain IP number

The library is lightweight (4kb uncompressed) & non-complicated. It just works by calling a function like:

yqlgeo.get('217.12.14.240',function(o){
  alert(o.place.name + ',' + o.place.country.content +
        ' (' + o.place.centroid.latitude + ',' +
               o.place.centroid.longitude + ')'
        );
});

will get you the city, country, latitude & longitude of any given IP.