Contribute to OSM

From GPSBabel

OpenStreetMap is a project aimed squarely at creating and providing free geographic data such as street maps to anyone who wants them. The project was started because most maps you think of as free actually have legal or technical restrictions on their use, holding back people from using them in creative, productive or unexpected ways.

If you're a GPSBabel user then you probably have a GPS. Why not use it to help this rapidly growing project?