The Newsapps Boundary Service is a ready-to-deploy system for aggregating regional boundary data (from shapefiles) and republishing via a RESTful JSON API. It is packaged as a pluggable Django application so that it can be easily integrated into any project.
For all the info you need on setting it up, read the installation readme.
This installation was set up--and shapefiles and definitions added--in preparation for the inaugural Hack Jersey hackathon in January, 2013.
To contribute to the source code:
This Boundary Service instance uses the following open-source software: