There are many ways of writing coordinates, and converting between the different ways is non-obvious but also quite trivial.
Hamburg ist eine der Geocaching Hochburgen Deutschlands. Innerhalb der Stadtgrenzen gibt es 841 aktive Geocaches (22.01.2008).
KisMap is a collaborative directory of wireless networks. It collects log files made with Kismet, a wireless network detector for linux.
QLandkarte GT is the ultimate outdoor aficionado's tool. It supports GPS maps in GeoTiff format as well as Garmin's img vector map format. Additionally, it is the PC-side front end to QLandkarte M (see next), a moving map application for mobile devices.