Witzenhausen is a small town close to Kassel, and there is a lot of local activism there. They have this Transition town initiative in the city http://ttwitzenhausen.de/, also the department of Agrarian studies of The Kassel Uni is located there. Apart from that the place is very beautiful, is located in the middle of castles and hills, and is famous for its cherry trees.
I believe if you come over to the Transition town office somebody from the activists will host you.
There is a free wifi in the university building on Nordbahnhofstrasse.
There is a free shop on the Bruckenstrasse.