Open Street Map
Open Street Map aims to produce street maps of the whole world, published under a creative commons license, which means everybody is free to use the maps however they want. The maps are created by people like you, and me. If you want to help create a map of your are, read the beginners guide, or you could Contact me.
I started mapping my local region, and I hope to expand, until I hit the edge of someone else's efforts. If many people do this, we will have a complete map of Britain very shortly :-)