Nice Map is a WMS client for Drupal. It comes with views module support and should work with latitude/longitude data stored by location module, or basic cck number fields.

Examples:
http://preparedness.interaction.org/
http://preparedness.interaction.org/foodsecurity
http://www.outsideindc.com/stumblesafely/
http://www.standagainstpoverty.org/en/events/map

WMS -> http://en.wikipedia.org/wiki/Web_Map_Service