Litrix.de: a website devoted to contemporary German literature, hosted by the Goethe Institut. Available in German and English, it contains information about authors and works, as well as substantial excerpts from works.
Gutenberg Project: an online collection of full-text books, including German classics (in both German and English).
Deutsche Literatur digital library: a large collection of full-text German works, to be read online or downloaded.
Zeno.org: a digital library that contains works in German from all major disciplines.
Sophie: a digital library of fiction written by German-speaking women between 1740 and 1923.
History of Germany: Primary Documents: a collection of links to German primary sources from the Middle Ages to the Present.
Zentrales Verzeichnis Digitalisierter Drucke: digitized German language collections.
German Studies Web: a portal maintained by the Association of College and Research Libraries, with a selection of scholarly resources in all fields of German Studies - literature, history, linguistics, etc.