The first place I ended up for advice was on Toytown Frankfurt and like most first time expats, I found it partly useful but not completely satisfying ;-). Hence the reason I have started this blog. There is definitely a lot of advice online and there have been 1000s of discussions in the Frankfurt section alone.
I would highly recommend you stop into Toytown as your first point of call for both local and general questions on Germany.
The trouble is that there is so much noise, distraction, arguing and partial information, that it can be a pretty frustrating process trying to find out anything concrete.
Still, as far as discussion groups go, it is pretty good 🙂