Gallivant

A simple GPS and map application utilizing maps from the OpenStreetMap project. Current features include automatic map downloading and user-placed map markers. Gallivant runs on Linux, might run on BSDs/OSX/Unix-y platforms (Let me know if you try it!), and almost certainly will NOT run (or even compile) on Windows.
Gallivant 0.3.0 showing its new POI capabilities.
Latest release is 0.3.0: Download source or a 32-bit Linux binary (which may well not work on your system).
Or, see what's new
Get Gallivant at SourceForge.net. Fast, secure and Free Open Source software downloads
Tiles Courtesy of the OpenStreetMap project and MapQuest