Wevideo is an web-based application that allows you to create videos. You can add images, videos that you took and gather them in a video and you can record your own voice or choose one of the theme musics for your video.
Teachers can use this app in classes, they can create animation and gather them in a video to make the subject more interesting.
Here is my Wevideo example.
Screencast-O-Matic is a web service that enables you to record your own computer screen while you are doing stuff and get it as an video. You can record your voice and let the “click” voices be heard.
It can be very useful for teachers. After an exam, you can record yourself and voice while explaining the questions and send it to your students or share it in the class with them.
Here is my record using Screencast-O-Matic.