OpenStreetMap data is made available for reuse under the Open Database License.
http://planet.openstreetmap.org/

Data download
This is almost 23 GB compressed or 150 GB uncompressed XML. 
http://wiki.openstreetmap.org/wiki/Download
ftp://ftp.spline.de/pub/openstreetmap

Country and area extracts 
http://download.geofabrik.de/openstreetmap/