This is a live demo that places GIS shapefiles onto a Google Maps overlay. In this sample, an Indiana County Boundary Polygons shapefile was loaded into a PostGIS/PostgreSQL database. This database was fronted by a map server, i.e. GeoServer, which was setup to serve map tiles for the map overlay.

This architecture permits you to manipulate what you want shown on the map purely in the database (with the full suite of spatial tools offered by PostGIS) and permits the map server to process, select, and place spatial content onto the map. It also performs the caching (and pre-caching) functions, so that as data changes in the database, you can ensure a speedy map, and control the age of the image data served.