When Google Maps, Yahoo Maps and finally Microsoft Live Search first released their mapping APIs, I was all over it.
The first map I built was the CapeLinks GPS Map with the Google Maps API in 2005. This tool allows you to get extremely accurate GPS coordinates for a position anywhere on the planet.
It outputs GPS coordinates with accuracy of up to 15 decimal places in the coordinates. This means decimal GPS coordinates with accuracy to within a couple feet (where Google Maps allows high level zooming in satellite view).
I also made a street address geocoder and map from the Google API and at the time it was one of the only street address geocoders on the internet.
From the email I received and from trolling the referral logs over the last five years, I learned that these GPS mapping tools have been used by government agencies, teachers, news stations, hunters, fishermen, hikers, photo geotaggers, real estate agents and all kinds of other people.
I created a database of over 3100 local Cape Cod waypoints from several different sources consisting of zip codes, villages, landmarks, historical sites, churches, waterways, nautical navigation waypoints, cemeteries, beaches, ponds, lakes, harbors, sandbars and dozens of other types of waypoints.