Interesting websites that are not so easy to find

The Citywiki Karlsruhe is the largest citywiki worldwide.

Carsharing with Stadtmobil

Where do the people live that have the same last name as me? Answer at Geogen!

The only free file synchronizer that actually works (even though the GUI is not really beautiful): Unison

OpenStreetMap is a free digital world map, which is more accurate than commercial services for many locations already.