Laptop GPS World
Forum specifically on laptop GPS
Geosoft
Introductory GPS info by Michal Schulz in the PowerPoint-style.
Kowoma
Extensive information on GPS and Geodesy.
GPS-Infoseite von Ralf Schönfeld
Lots of information and practical tips around the topic of GPS
NaviBoard
Forum specifically on the topic of GPS (devices, software etc.)
GpsPaSsion
Lively forum around GPS HW & SW.