I have just found this website run by ADAC(The German AA).It shows many camping sites including municipals through out europe.
1. click on "Ziele?"
2. enter the name of the city or region where you wish to stay (please observe the German spelling, ie Koeln for Cologne, Muenchen for Munich etc.)
3. click on any of the blue search result(s)
4. you'll be shown an interactive map of the area with campsites indicated in blue and red triangles (tents). Red campsites are seasonal and blue campsites are open all year.
5. click on "Campingplatzbeschreibung" in order to access further details, including opening times, phone/fax numbers (please dial 0049 for Germany first and drop the 0 on the area code) and, if available, an email and web address