Ground Game, from Moonshadow Mobile, is an amazing mobile phone based canvassing tool that gives access to current registered voter information via Google Maps. The tool provides political canvassers with maps of the neighborhood they are walking that show the locations of individual houses containing the voters they are targeting.
With the application you can view relevant information about voters. The application also allows campaign managers to track in real time the location of canvassers on the ground. To view the full capabilities of the application you really should view the video above.
From the same developers as Ground Game comes this Google Map of Oregon's 1.8 million voters. Using the map you can zoom in on any area of the state and instantly see voter density and voter registration.
The Voter Mapping site uses the technology that was developed for the Ground Game app for political candidates.