Google maps can be used not only for displaying maps, witch is it's initial purpose, but can be used for many others purposes.

Then working with France client's i had some two interesting projects one was for displaying some company network data. Like contracts addresses and another one display network of pipes. Data was imported using GPX files. They both were realized using Google maps. Because of privacy policy i cannot tell more, but in general Google maps was used in two ways:

1. Displaying contract's locations.
2. Displaying network pipes.