Edmodo

Edmodo is a free, secure, social learning platform for teachers, students, schools and districts. It provides teachers and students with a secure and easy way to post classroom materials, share links and videos, and access homework, grades and school notices. Teachers and students can store and share all forms of digital content – blogs, links, pictures, video, documents, presentations, and more. There are also special institutional features for schools and districts that can be accessed for free by administrators

http://youtu.be/TzPHQr1ONaA
http://youtu.be/9tTU1iUfExk
En español: http://www.edmodo.com/?language=es#