Malkin and I are thinking about a Germany bike trip in the Spring. I did some looking around and found this source for maps:
http://www.esterbauer.com/rtb_uebersicht.html
They are all in German, but I speak German and Malkin is learning...
We bought the "In and Around Munich" book from amazon.com and are finding it both informative and delightful!

There is also a German version of the bike forums:

http://radreise-forum.de

Again, it's mostly in German, but many/most of the folks there also speak English. It took me about a week to get registered (mostly waiting for their response), but it appears to be a pretty helpful place.

Prost!