Google Map Maker

Google Map Maker is a Google Maps service that allows you add or edit features, such as roads, businesses, parks, schools and more. Using Google Map Maker tools, you can visually mark locations and add detailed information about these locations. Once you have submitted content, this information may be edited by other users or moderators. At a later time, this content may be published in Google Maps for others to see and use.

Link:
http://www.google.com/mapmaker