The openlayers module and its submodules allows users to combine maps from different providers into drupal. It is a very powerful module capable of building geo applications in drupal.

I have used it in one project so far to build an application that renders apache solr search results on a map and I definetly recommend this module to build geo apps. The quality of code is very high, it has a good api and the OpenLayers JavaScript library is open-source, making it flexible and capable across standards as well as proprietary APIs.

http://drupal.org/project/openlayers [5]