Google’s latest initiative is called Open Spot. It’s an Android (2.0 and up) application that allows you to search for unclaimed spaces that have been reported by other Open Spot users. Once users head elsewhere, it allows you to mark your spot as open and available. Once a spot is marked, the color gradually goes from red to yellow the longer it remains unclaimed.
Engadget checked it out and they generally like it, however they feel that the ability to add notes to each marked place is needed. There should be a way to see whether a spot is metered, covered by a strange city permit law etc. Hopefully an update will enable comments.