Three bilingual dictionaries A dictionary based on a user-built corpus, published by Paul Hemetsberger, with a ‘vocabulary trainer’ (flash-card simulator).

BEOLingus, published by the Technische Universität Chemnitz. A dictionary published by Michael Kellog, accompanied by language discussion forums.

Two monolingual dictionaries

Das Digitale Wörterbuch der Deutschen Sprache des 20. Jahrhunderts, von der Akademie der Wissenschaften

Das Deutsche Wörterbuch von Jacob und Wilhelm Grimm, begun in 1854.  Extensive documentation of changes in the meaning of German words.

Noch was dazu?

A long list of dictionaries and other resources is maintained at