How I Use It
Most of the use of Edmodo has been while working on projects with students from around the world. This is simple for teachers to join and easy for students to understand. They love the "Facebook" feel to it, but I love the security safeguards around it, such as students can only post to the public areas or to a teacher, teachers can get emails of all students' posts, and many others. I use this to teach about digital citizenship.
I think all elementary teachers should be using Edmodo. It is an easy, quick tool to use and there are many advance features for teachers who want to take it further. Students love it. The organization within a group could use some work. The chronological order of things work, unless you have a very active group. I wish there were sub-sub-groups. I also wish you could favorite a post in case you want to go back to it.