The WFS Server module for Drupal will allow geographic information systems (GIS) to query Drupal sites about geodata they are storing and then communicate it back using the Open Geospatial Consortium standard for Web Feature Services.
Features
Read more in the blog post: Drupal as a WFS
Requirements
It will use the location module as an API to store all of the geodata associated with nodes.
Demonstration
An alpha-quality demonstration of the capabilities is online at http://geodaniel.org/wfs?request=GetCapabilities though it should be noted that it doesn't work yet ;)
Download
The code is still being worked on and is not yet available