Harnessing the wealth of OpenStreetMap data, MapQuest has launched an "Open" version of itself, allowing anyone to add restaurants, fix errors, define the best directions that real drivers know, and otherwise improve the mapped world around them.
If there was any way MapQuest could differentiate itself from the seemingly ubiquitous Google Maps, this is a pretty good stab at it. OpenStreetMaps has more than 300,000 registered users worldwide, and offers results that speak to both local knowledge and dedicated contributors' fixes. Not every area is quite so filled out, of course, but you can learn a thing or two looking around the Open version of your city. And if you don't like what you see, you can file a bug.
MapQuest Open is free to use, and free to edit and modify.