Screencastify is a screencasting extension for Google Chrome. It allows you to record your screen activity for creating tutorials, etc, and runs entirely in Chrome, so opens the possibility of screencasting up to Chromebook owners. Here's how to use it:
Getting Started
Recording Basics
Saving & Sharing
Helpful Information:
If a video is not playing, you can always download it by clicking the download button in the upper-right corner of your window:
(In order to see the button you may need to move your curser to the upper-right corner of you screen).
Once it has downloaded, you can play it by clicking on the video in the bottom left hand corner of your browser window.