viking is a free/open source program to manage GPS data.

You can import and plot tracks and waypoints, show Google maps and/or
Terraserver maps under it, download geocaches for an area on the map, make new
tracks and waypoints, see real-time GPS position, etc.

It is written in C with the GTK+ 2 toolkit, available for Linux, other POSIX
operating systems, and Windows, and is licensed under the GNU GPL.

WWW: http://viking.sourceforge.net/