I introduced my first year German students to Duolingo this week. They loved it! Few of them had seen it before, and they were almost immediately hooked by the friendly green owl. It was great to see some of my reluctant students getting excited about it. One of my students with special needs who is struggling to keep up commented to me that this was really helpful to him. Jawohl!
I've know about Duolingo and enjoyed it for some time (I'm learning Spanish to keep up with my son) but haven't used it much in the classroom because of the inconvenience of reserving the computer lab and bringing the whole class down there, getting everyone set up, etc.
But now that we are 1-1, it's definitely worth it to have all of my students create an account and try it out. It's on my list of activities that students may do when they finish their work early.
Hopefully I've got them hooked so that they'll even do it outside of German class!