Screencast.com is a free, secure hosting option that can allow you fast visual communication if you don’t have an FTP site. Screencast will give you up to 2 gigabytes (GB) of storage and 2GB of bandwidth per month, and you decide how private or public to make your files.
Limited Space Warning!
A gigabyte is about 1000 megabytes which means if you have 10MB video files, you could upload 100 of them for free. This also means that about 100 different people could view 1 file each month for free. As you can see, this becomes a problem if you are a teacher with more than 100 students.
Therefore, I recommend you (teachers) upload your content to an FTP site. Your students, however, can share files with you through Screencast.com for free and chances are you will never use up the free bandwidth.