http://de.thefreedictionary.com renown free dictionary with lots of examples and explanations in German
https://www.dict.cc crowdsourced dictionary targeted primary on GE <> different languages and EN <> different languages.
http://www.duden.de Holy Grail of German dictionaries online for free
https://www.dwds.de another powerful tool for word digging
http://www.linguee.com
http://www.verbformen.de German verb conjuration