FoxtrotGPS is a fork of Marcus Bauer's TangoGPS project, with a focus on 
cooperation and fostering community innovation.  It is a lightweight moving
map application that can be used with or without a gps unit.  By default,
maps tiles are downloaded from the OpenStreetMap project, but other sources 
are available, and new ones may be added.

Map areas may be downloaded and cached for use while offline.

WWW: http://www.foxtrotgps.org