For anyone with an iPhone, this might be practical. My SO has one, and it uses google maps and the GPS to locate dog parks near you. Unfortunately, it doesn't have every one... it's missing the two closest to us, but it has an option to send in parks, so the more people who use it, the more parks will pop up.
Here's an article about it: http://www.iphonesavior.com/2009/01/review-iphone-off-leash-dog-park-locator.html
It's going to come in very handy when we travel with Dexter.