gpsd is a service daemon that monitors one or more GPSes attached to a host computer through serial or USB ports, making all data on the location/course/velocity of the sensors available to be queried on TCP port 2947 of the host computer. With gpsd, multiple GPS client applications (such as navigational and wardriving software) can share access to GPSes without contention or loss of data. Also, gpsd responds to queries with a format that is substantially easier to parse than the NMEA 0183 emitted by most GPSes.
Viking is a free/open source program to manage GPS data. You can import and plot tracks, routes and waypoints, show OpenStreetMap, Terraserver, Bing Aerial and other maps in it, download geocaches for an area on the map, make new tracks and waypoints, geotag images, see real-time GPS position, etc.
Moritz Stoll: Christine Thürmer ist die meist gewanderte Frau der Welt. Sie lebt vom Langstreckenwandern, schreibt Bücher und versorgt ihr Follower von Unterwegs mit
H. Fliegel, and R. DiEsposti. Proceedings of the 28th Annual Precise Time and Time Interval Systems and Applications Meeting, page 189--200. Reston, Virginia, (December 1996)