I have just uploaded a couple of videos onto youtube going through some German grammar. At the moment I have done accusative and dative pronouns and adjective endings following indefinite articles.
One of my Yr 10 students made this grammar tutorial on Relative Pronouns without much guidance from me. This isn't a topic that I normally teach at Year 10 level so I'm very impressed!
Wow - you should join this site if you are a German teacher/learner! It has LOADS of online activities to practise your German not to mention current topics and competitions! Check it out!