I'm a big fan of the work Development Seed puts out. Recently they released Nice Maps. Nice Maps is a Drupal module that allows you to use an external mapping feed, and overlay the map with other useful data unrelated to the map itself. I've yet to try this out, but plan to soon. Here's a nice short screencast highlighting how to use it.

http://s3.amazonaws.com/video.devseed/nice-map.mp4