Screencasting from Chromebooks is one of the top items in the wishlist for Chrome OS users. If you are ready to play around with your Chromebook a little, you can do this now. Else, wait for the feature to land on your Chromebook in its full glory.
You will need your Chromebook in developer mode ( not developer channel), crouton and a script which asks the Chromebook to start screencast.
A shameless copy and paste from François Beaufort:
1. First you need to make sure your Chromebook is in Developer Mode. Select your device at www.chromium.org/chromium-os/developer-information-for-chrome-os-devices to know what to do.
2. Then, open a Chrome Terminal by pressing <Ctrl> + <Alt> + t.
3. Visit the crouton website at https://github.com/dnschneid/crouton, download crouton from http://goo.gl/fd3zc and create a chroot environment by running sudo sh -e ~/Downloads/crouton -t audio
4. Finally, download the screencast.sh script from http://goo.gl/UmWAta and run sh -e screencast.sh
Tada¹, you can now record what’s happening on your Chromebook!