The GeoEncoder plugin plots a post's responses on a Google Map, and can list them by distance from the original poster. When it is enabled, on a post detail page, click on "Response map" and "Nearest responses" under "GeoEncoder" on the sidebar menu.
Clone this repository in the webapp/plugins/ directory of your ThinkUp installation.
The GeoEncoder plugin uses the Google Maps API to store latitude and longitude points for each post and user. In order to access the Google Maps API, you need to set an API access key, available for free from Google.
To configure the plugin, sign up for a Google Maps API key, and enter that key into the GeoEncoder plugin's options area. Choose whether you want to see distance in kilometers or miles, and click on the "Save Options" button.