I've been reading quite a bit recently about gis and mapping with drupal, recently. I've never used drupal to manage a gis system before - only done it with Plone and from-scratch one-offs. Track my progress at map.archi.st
I see a lot of need in Detroit for accessible and customizable geographic databases, especially for community groups working in far-flung hoods. The Detroit Agricultural Network is a perfect example of this: they support tons of gardens all over the place, and many people may not even know that there's a community garden only a few blocks away from their house or workplace. Just gotta hook whatever systems up to a shortcode sms gateway....
A good lay-of-the-land overview of drupal gis can be found in this Lullabot podcast
Looks like the Chicago Tech Collective is involved in some drupal gis module development. Here's one of the projects that resulted: a Chicago library site with a bunch of different datasources squeed into one somewhat useful interface. Novel!