Openstreetmap and City Wiki
After I had moved to Karlsruhe for the second time I was astonished, when I figured out, how densely Karlsruhe was covered in Openstreetmap. I'm sure it is better covered there than in any commercially available map (including google maps) and I can not think of any road or even path in one of the city's forests that is missing. Sometimes it's even too dense, as a route search for pedestrians results in a route that includes paths that are paths but that are barely acceptable, especially during bad, rainy, weather. The second city related project where some people must have worked very persistently to collect all the information is the city wiki (Stadtwiki). It's not only useful, if you're new to the city, but it actually helps to inform people on ongoing projects in the city, at least it could help, if you take a look there. It is said that this city wiki is the largest in the world. These two and some other projects and clubs gave me the impression that there must be quite a number of people in the city, who just can't sit still.