Here's a link to the Germany tourism page. It has an interactive map where you can click on the main cycle routes, of which there are many. If you then click on "further information" at the bottom of the new page, it takes you to another page, where, on the right hand side, there is often a link to a downloadable PDF which gives an overview.
Very handy.
http://www.germany-tourism.de/cyclin...ermany_map.htm