Currently available only in the U.S., Canada, and the Netherlands, Open Spot is a Google Labs project that aims to help Android OS users with parking. Relying on a mix of community spirit, Assisted GPS, and Google Maps, Open Spot plots out open parking slots within a 1.5km (or 0.9 miles).
Each plot is color-coded to reflect "freshness"—or when they were declared as open—and eventually disappear of the grid after 20 minutes. When the user pulls out from the parking slot, they can now mark it as open for other Open Spot users.
Clearly, Open Spot is a great idea but will only become truly useful if end users contribute to its cause. This means interested users who want to see the service fly will have to evangelize the app to friends, family, and other Android OS users. At least Open Spot is a free download available from Google Labs.