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.
Nimbus is an extension for Google Chrome that allows you to screen capture FULL Web page or any part. Edit screenshots. Record screencasts - record video from your screen. Capture the web page, either part of it or the whole browser window, edit your screenshots in a very user-friendly interface.