What began as a simple mapping application has since turned into one of the most versatile tools on the Web. Google Maps is inspiring developers to create customized maps of just about everything, from taco trucks in Seattle to scuba sites around the world. Google Maps debuted in beta form in February 2005, and in October was integrated into Google Local search, allowing users to plot businesses on grids and later on 3-D satellite images of cities. More significantly, the application programming interface, or API, went public in June 2005, inspiring developers to use the free tool kit to create innovative mashups. One of those, HousingMaps.com, impressed Google so much that it hired the site’s creator. “Finding high-quality developers has made the API worthwhile for us,” says Google product manager Thai Tran. Google also reserves the right to advertise on any maps that use the API. After all, notes judge Norman, who is also co-founder of the Nielsen Norman Group, “Google isn’t just a search engine; it’s an advertising company.”

BOTTOM LINE: Since Google Maps was integrated into Google Local, the number of unique monthly visitors has increased 38 percent to 17.9 million.