Scott Cariss

This plugin is meant to be used by other developers and to be used together with themes and other plugins. Many themes and plugins use WordPress meta data table to store longitude and latitude co-ordinates for posts. While this works fine the meta data table cannot be indexed very well. Let’s take for example you have made a custom post type called ‘properties’. You create 100,000 posts all attached with latitude and longitude co-ordinates. You want your users to search for those properties in a 50 mile radius for example. Because of the method of which WordPress stores the meta data the query is slow especially when dealing with large amounts of data.
This plugin has been made to retro fit your current WordPress install. You as the developer select, using filters, what meta data you want to start capturing and this plugin will put the data in a table better optimized for storing latitude and longitude co-ordinates. Upon plugin activate existing data will be index and any data from then on.
Usage: 
Before activating set what meta keys you want this plugin to capture by using the filter ‘sc_geodatastore_meta_keys’. Your latitude and longitude values have to be stored in a single meta field like: <code>51.507334,-0.127682</code>
Example usage of the filter:
<pre><code>add_filter( 'sc_geodatastore_meta_keys', 'homes_for_sale_geodata' );
function homes_for_sale_geodata( $keys )
{
 $keys[] = "properties_address_coords";
 return $keys;
}
</code></pre>
Notice: 
This plugin is currently limited to only allowing one pair of co-ordinates per post. Maybe in a later version I will allow multiple pairs per post, but since this plugin was made to serve my purpose and it serves it well I see no reason to build upon it yet.

Geo Data Store

Stores lng/lat co-ordinates in a better optimized table. This plugin is meant for the use of other WordPress theme and plugin authors

BMLTGuy

This plugin is really meant to be an aid to folks doing data entry, and trying to find locations with Google Maps. 
It shows two forms: One on the left, and one on the right. The left form allows you to enter address information, or a longitude/latitude pair, and the right form shows the result of a geocode lookup or a reverse geocode. 
It is possible to display an interactive map, and also to examine the raw JSON data sent back from the geocode/reverse geocode lookup. 
This is an extension of a utility that was written in order to help data entry personnel enter accurate address information. 
It has administration options (“Geolocator Options”, in “Settings”). 
The plugin outputs highly optimized code that is XHTML 1.0 Strict compliant, as well as WAI AAA.
<h3>Usage</h3>
To use this utility, you simply enter address information into the fields in the left-hand form. You can enter all the information in one line, if you wish. 
The string that is displayed above the entry is what is actually sent to Google Maps to be geocoded. Once you have filled in the address, click on “Address Lookup”. This will send a geocode request to Google Maps. 
The response is parsed, and shown in the right-hand (gray) box. A set of arrow links will appear between the two forms. These allow you to easily transfer results into the entry form. 
If you enter a longitude and latitude value into the bottom two boxes in the entry form, you can do a reverse geocode. This asks Google Maps to figure out an address, based on the values in these boxes. 
In many cases, Google Maps will return more than one response, and you can cycle through these responses. 
Each response shows an “accuracy” number in a scale, above the response. The more accurate (confident) the result, the closer the scale marker will be to the right. 
In the interactive map, there are two markers shown. The yellow one reflects the long/lat pair in the left window, and can be moved around. Clicking in the map will move/create the marker, and fill in the long/lat fields. 
The gray marker reflects the position of the current response, and cannot be moved. 
The raw data window shows the entire response from Google Maps, presented in a hierarchical fashion. If there are more than one placemark, each mark will have a link that will bring that mark into focus in the gray form.

Geolocator WordPress Plugin

This is a plugin that displays a "worksheet" for verifying and researching addresses with Google Maps.

Geo Data Store vs Geolocator WordPress Plugin