Google Map Maker

POWER TIP

If you’re in the U.S., you can now add your expert local knowledge to
Google Maps with Google Map Maker for the United States. For example,
you can get started by adding the outline of the soccer field at your
local park, or marking that a local two-way street recently changed to
a one-way thoroughfare. Each edit in Map Maker is reviewed, and after
approval, will appear in Google Maps within minutes. Using Map Maker,
people have built out and edited the maps for 183 countries and
regions around the world; now you can ensure the places you care about
in the U.S. are richly represented on the map.
http://www.google.com/help/mapmaker