NYTimes.com: New York City Building Permits Google Maps mashup:
The New York Times Real Estate website mashes up Google Maps with a list from the NYC Department of Buildings to show New Construction, Demolitions and Major Renovation projects.
SF Bay Area Real Estate Google Maps mashup - From the creator: "..We put "motivated" sellers, "short sales" and price drops on the map, with data pulled from the local MLS
Google Maps showing Dallas Neighborhoods - Look to the bottom of the page for the Maps implementation.
Google Maps mashup helps you answer: Where Can I Trade Different Futures Contracts?
US Tennis Courts Google Maps mashup - Lists courts by city with the ability to add new cities and courts.
A fun one: Downtown Savannah, Georgia
More fun: Joe Cool Summer in Santa Rosa, California - Check here for more details.. [Thanks Amy!]
US Winery Tour Planner gets an update - From the creator: "..We have incorporated Google Directions and Google Local Search Control. Our printable Google directions include the contact information for each winery in the itinerary. We also display the total estimated driving time and mileage as a user develops their tour."