We have multiple populations of patients spread out over geographic distances. For each population, we want users to easily define non-overlapping polygons. The outer borders are likely to be U.S County boundaries, if that makes any difference.
Essentially, I'd like for users to visually build groups of non-overlapping polygons and have the application provide us with sets of coordinates for each polygon. I would then be using the data in Google Maps. We currently have a method to identify patient's location by lat/long, using Google Maps API if the user needs to approximate the location.
Web-based software is preferred, but I'd consider a desktop package if the interface was easy enough for our users with minimal training.