Viking is a free/open source program to manage GPS data
... the open-source glide computer
A Guide of the Trees of Barcelona City
Build your own GPS unit
A C library for parsing/normalizing street addresses around the world
A gui for linux users of miniHomer, a GPS tracker
Aircraft navigator with HSI for TomTom devices
Visualize data from the opencellid.org project
a free and open map of wireless communicating objects
In-flight navigation (and more) for private pilots (Linux).
GPSBabel converts and transfers data like waypoints, tracks & routes.