For general information about MBA programs worldwide in German language, I recommend the MBA-Gate website. The annual MBA Gate Expert Panel is the biggest information session in Germany by independent organizers and therefore highly recommended. I will also be a featured speaker in the next event!
For GMAT preparation, I recommend to attend the course from Manhattan Review. On this website you also find information about the TOEFL.
In case the German dates are not convenient for you, you may also check out the Manhattan Review's main website for their London courses.
Unrelated to this, here is some other cool stuff from Joern Meissner:
MBA Candidate, NYU Stern Class of 2005
I hope I soon will have time to publish some more information here, but here are some basic guidelines for MBA applicants from Germany, as I have gotten quite a few requests in the past: