Duolingo is a popular free service that offers activities for learning Spanish, English, French, Italian, Irish, Dutch, Danish, German, and Portuguese. The service works in your web browser and is available as an app on Android, iPad, and Windows 8. Last winter Duolingo introduced Duolingo for Schools. Within Duolingo for Schools teachers can create online classrooms in which they monitor their students' progression through the learning activities available in Duolingo.
In the video embedded below I provide a demonstration of how to create a classroom in Duolingo for Schools. The video also shows a student's view of Duolingo for Schools.