Viking is a free/open source program to manage GPS data. You can import
and plot tracks and waypoints, show Terraserver maps under it, add 
coordinate lines, make new tracks and waypoints, hide different things, 
etc. It is written in C with the GTK+ 2.

The following options can be enabled (by default, they are disabled):

MAPNIK=yes     for rendering with Mapnik (requires mapnik)
GEOCACHES=yes  for geocaches acquire
