Free- This app is a great app for classrooms with iPads. Not only is it great for iPads, but for any classroom with good access to the web. When you login to Edmodo, it looks very similar to a Facebook account, but the best part is that students do not have access to post on anyone's wall besides the classroom teacher and the entire class. There are so many ways that you can monitor and control what your students are doing on the sight.
Edmodo can be used in so many different ways, but another way that we use it is for assigments. I will create an assignment in Edmodo and send it out to all classes via a post on the classes wall. The students will click on the assignment, complete it, and turn it back in all on Edmodo. I then get a nice little organized system to grade th assigment and provide communication to the student.
I am sure that I am just scratching the surface on the potential of Edmodo, but it is a great tool to start using...if you aren't already!