Only for certain countries at the moment.
Google Map Maker is a significant step in our ongoing efforts to engage Google Maps users and equip them with an easy-to-use tool to build high quality maps of their neighborhoods, cities and countries. Map Maker allows you and your peers to add, edit and moderate most features you see on maps including roads, lakes, parks, points of interest, businesses, cities and localities. You will be able to trace many of these features using satellite images; as you trace, maps are immediately updated.