Drupal is a popular, free (as in freedom), highly extensible web content management system with a large development community.
Althought web development is not my core business I had to deal with it in a project for the European Commission's Joint Research Center where I was engaged as the GIS expert from late 2009 to late 2010.
As soon as I realized that the use of Drupal was actually a _requirement_ for the deliverable (it took a long time, but this is another story), I disposed the prototype backend based on symfony / postgis and focused on networking with existing communities around Drupal and geographical information management.
In June my proposal to host a drupal-geo mailing list on the Open Source Geospatial Foundation infrastructure got positive feedback, from both the drupal and osgeo communities.
In July I became co-maintainer of the Drupal-OpenLayers module.
Notable contributions to the OpenLayers module have been been dynamic styles support and clustering behavior, both aimed at making it feasible and easy to represent several hundreds spatially-featured "nodes" (content units in drupal jargon) on a map with a few clicks. Plus a bunch of other bugfixes and minor improvements.