Slate has a new feature called “Map the Candidates.” It looks like they just track where the candidates are going, and then plug the towns into Google Maps. You can also select which candidates are on the map, and you can adjust the time parameters.
It’s an interesting, useful feature, but it looks a little cluttered. Here’s the link, and here’s a screen shot of all of the candidates nationwide in the last week, and one of John Edwards in Iowa. Click on the maps for a full-size, less-blurry image.