With Slashgeo using Drupal since 2010, I recently found Cartaro, an open source geospatial CMS.
The overview: "Cartaro is the web mapping platform that brings the power of the best open source geospatial components into a content management system. With Cartaro you are able to set-up and run your own geo-enabled and OGC standards-compliant website with not more than a few clicks. The geospatial components used in Cartaro are PostGIS, GeoServer, GeoWebCache and OpenLayers. All those are managed from within the powerful CMS Drupal.
Cartaro is for organizations and individuals that need to run a light-weight spatial data infrastructure (SDI) without the need for extensive configurations and much individual programming.
Cartaro is also for all websites that focus on CMS features while also having to handle geospatial data."
If you head to the project's page on Drupal, only a dev version for D7 is currently available, but it looks in very active development. We did mentioned other Drupal geospatial projects in the past, including the CartoDB Drupal module.