Really good supplemental, to Duolingo, sites
I found Deutsche Welle, a German news and media site, that is a really good addition to duolingo. They have a whole section devoted to courses to learn German @ http://www.dw.com/en/learn-german/s-2469. They have grammer, vocabulary audio and some video as well. I really like their news mp3. They are spoken more slowly especially for students and the speakers use very good German, no dialect, slang... Also, on their main page http://www.dw.com/en/top-stories/s-9097 , on the main banner there is a link/hover "learn german" that has a lot more materials. (videos and mp3's seemed to worked better in firefox than chrome for me). Also BBC on http://www.bbc.co.uk/languages/ has German language courses. Actually, they have about 40 languages available. The Free BBC german lessons link is on http://www.bbc.co.uk/languages/german/ . They too have video, audio, grammar... The page has also alot more info/links for other scources for learning German. http://www.deutsch-lernen.com/ ; http://www.deutsch-lernen.com/learn-german-online/beginners/summary.php this one has alot of grammer, vocabulary and rules. Not as much, less like a game, fun but very thorough.
Thanks for those.
I would also suggest two great FREE supplements to Duolingo German:
Vocabulary: Memrise workcards originally created by Duo user Bakpao. These cards follow the Duo course and I found them invaluable at helping me learn the vocabulary properly as I went through each skill on the course. http://www.memrise.com/course/335725/comprehensive-german-duolingo-vocabulary/
Explanation of grammar and verbs : Language Transfer Complete German. This is a free audio course which explains how German works, using a method similar to that of Michel Thomas. http://www.languagetransfer.org/#!complete-german/c1m0e