One good example for this successful cooperation is the Federal State of Rhineland-Palatinate with the city of Speyer. During the CHAMP project Speyer has started its integrated sustainability management system. Actually they are elaborating the indicator set for their Baseline Review. There is a ppt available about the local development of Speyer in the cities solution section.
Another German example using IMS fighting Climate Change is the City of Nordhausen in Thuringa. Stakeholder Integration and public participation are crucial for the local responsibles. Therefore they organised in cooperation with ICLEI, two stakeholder fora and a public information event. Further information you get here.
An interesting source for further information on local sustainability in German is the webportal nachhaltigkeitkommunal.eu.
Do you know any other good examples of German cities being active fighting climate change and fostering a sustainable future?