Germany and Surrounding Areas, Address Books 1829-1974
(they have translated "Adressbücher" as "Address Books" although we would call them directories.)
Indexed using OCR, and some don't seem to have been indexed at all, so if you don't find someone by searching, try browsing instead.
This is the link to the whole "German Historical Directories" collection as they already had quite a few:
http://search.ancestry.co.uk/search/group/germandirs