Edmodo is a private micro-blogging platform built for use by teachers and students for use in the classroom.
The problem with traditional web 2.0 tools in a k-12 classroom environment is concerns over privacy of the students. Edmodo has been built with the privacy of students in mind.
Edmodo provides a way for teachers and students to share notes, links, and files. Teachers also have the ability to send, alerts, events, and assignments to students. Edmodo also has a public component built by allowing at the teachers discretion to post any item to a public timeline at the teacher’s discretion.
Access it here.