Using the Google Places API you could output the different
establishments in your area. You can't search for a specific type,
though. Instead you could filter the results by their "type"
attribute. See more on:
http://code.google.com/intl/en/apis/maps/documentation/places/#PlaceSearches
I'm not sure if it outputs tennis courts and is limited to 20 results
per search query, but at least it's better than nothing ;-)