The German Digital Library (Deutsche Digitale Bibliothek) is a kind of national portal for the digital collections of all the participating libraries from Germany, though unfortunately not all take part in this endeavor. Nonetheless it is for me a very helpful tool to get a first overview of what has been digitized so far. One particular useful feature that I am using regularly are the so called "Favoritenlisten", lists of favourite entries from the catalogue. These lists can also be made publicly available.
I am at the moment interested in Robert Burns and his reception in Germany during the 19th century so I created a list of the German publications that are available there at the moment: translations, secondary literature and sheet music.
Here are a handful of translations (Kaufmann, Gerhard, Heintze, Winterfeld, Bartsch, Silbergleit) as well as some musical publications. Particularly important and interesting are F. W. Jähns' Schottische Lieder und Gesänge (1836), one of the earliest collections of new musical settings for German versions of Burns' poems and songs and Hermann Ritter's Altschottische Volksweisen (1887), one of the few editions including not only the original English words but also the original tunes.