Frankfurt, Munich and Dortmund are completely sold out. There are some tickets left for Munich when you want to buy a package
expensive ticket/expensive hotel for 179 euros

http://www.eventim.de/cgi-bin/tnl.dll?evid=216754&p=t050117

There is no such offer for Dortmund. Frankfurt, which is sponsored by HR3 (radio) is officially sold out.

There are few tickets left for Leipzig and Hamburg

Thanks to YourValentine for this information.