I found OpenStreetMap – project aiming to collect geographical data (like city plans) and provide them on CC license. It is volunteer project, gathering data via GPS log files upload.
It looks like area coverage is mainly in UK, but as service will grow, it will cover much more areas. It is free service, and I wonder how they plan to cover cost of hosting. GIS data can be quite large, and fees for storage and bandwidth will be increasing over time, when database will grow. Bigger database means much more useful, and more users.
Any way, nice idea, I wish I had some GPS unit, I would provide some data from Warsaw…