Wikipedia
GPSBabel
GPSBabel is a cross-platform, free software to transfer routes, tracks, and waypoint data to and from consumer GPS units, and to convert between over a hundred types of GPS data formats. It has a command-line interface and a graphical interface for Windows, OS X, and Linux users.
GPSBabel is part of many Linux distributions including Debian GNU/Linux and Fedora, and also part of the ' fink' system for getting Unix software on Mac OS X.