Google Map

www.housingmaps.com
One of the most useful mash-ups, 3D software engineer Paul Rademacher's creation was born of frustration. He needed to find a house in Silicon Valley for his job at DreamWorks Animation and grew weary of the piles of Google maps for each and every house he wanted to see. So he created a Web site that mashes up listings from the online classified-ad service Craigslist with Google's mapping service. Choose a city and a price range, and up pops a map with pushpins showing the location of each rental.

"I wanted this to be a real application, not just a Web page," says Rademacher. "The key will be what's useful, not just what's cool." His site has spurred a rash of Google Maps mash-ups, including some of the following slides.