Came across this article in Directions where the Ontario, Canada chapter of URISA offered a prize for the best open source application.  GIS Applications Specialist Denis Lalonde of the City of Cornwall won the Gold Prize using the MapGuide (http://mapguide.osgeo.org/) open source development framework for web mapping.

Here is the link to the resulting web map: http://maps.cornwall.ca/mapguide/cornwallmaps.php

What is in your Open Source toolbox?