OpenStreetMap: editable map of the whole world
I really like this project, and was quite impressed by the quality of maps!
OpenStreetMap is an editable map of the whole world, which is being built largely from scratch using GPS traces, and released with an open content license. The OpenStreetMap License allows free (or almost free) access to our map images and all of our underlying map data, and the project aims to promote new and interesting uses of this data.
OpenStreetMap allows you to view, edit and use geographical data in a collaborative way from anywhere on Earth.
Check out the wiki if you want to get involved in the process.
View of Zürich city