Editable Google Maps
Depending on how well they can deal with spam, and how open they make it, this could be a big deal. Google are letting users edit locations in Google Maps.
Having done my fair share of adding geolocation information to Freebase recently, I’m quite interested in open mapping technology. Google Maps does allow you to get latitude and longitude coordinates—to get the center of the map, run gApplication.getMap().getCenter() from JavaScript while using Google Maps, and you’ll get an object containing that data. I’m not sure that they have an API that lets you get at it more reliably, but there are other services which will let you do so.
You can also give Google Maps latitude and longitude as inputs, which makes all of this even more useful. Really, I begin to think that any location, and especially any location run by public services (such as transport) should be providing the geolocation of all their facilities (including every stop) as a part of their base service. I’m quite convinced that good would come of such efforts.