Recently, I had an opportunity to take advantage of Google's Fusion API along with their Map API to produce IDX listing maps for a client that is a real estate broker.
The system uses the client's IDX listing data as a source for a Fusion table that is updated every day. When the clients web site is used to show listing for a particular area, the system uses the Google MAP API along with the Fusion table id to produce a map with listing for the area that is displayed along with the property list.
I'm expecting to be working out the kinks as issues pop up but all in all the thing went together pretty fast and has been running with a minimal of tweaks for over a week now.
Below is the raw Google Fusion table displayed in an iframe using a map visualization.
You can check out the same Google Fusion table with the Google Map API layer implementation by clicking here. If you compare the info windows (click on a map pin) from the two maps you will see how I improved the display using the Google Map API.