Cross platform (lin/win/mac) geographical information system (GIS)
Accurately Locate Smartphones using Social Engineering
Traccar GPS Tracking System
... the open-source glide computer
Combines the high accuracy of AR with the scale of GPS data
Library for OpenStreetMap offline rendering and routing
Multiplatform Ham Radio APRS and Mapping Program
GT2 combines online and offline navigation for hikers and cyclists
Interactive geospatial directory
a free and open map of wireless communicating objects
In-flight navigation (and more) for private pilots (Linux).