GPSBabel converts waypoints, tracks, and routes from one format to another,
whether that format is a common mapping format like Delorme, Streets and Trips,
or even a serial upload or download to a GPS unit such as those from Garmin and
Magellan. By flattening the Tower of Babel that the authors of various programs
for manipulating GPS data have imposed upon us, it returns to us the ability
to freely move our own waypoint data between the programs and hardware we
choose to use.
It contains extensive data manipulation abilities making it a convenient for
server-side processing or as the backend for other tools.

WWW: http://www.gpsbabel.org/