Asus C200 Bay Trail Chromebook: Dev Mode and Ubuntu
http://liliputing.com/?p=65961
http://www.amazon.com/gp/product/B00K...
Update: As noted near the end of the video, while Ctrl+Alt+Shift+FWD key will let you switch from Ubuntu to Chrome OS, pressing the keys again will freeze the system. To safely switch from Ubuntu to Chrome OS, just log out of your Ubuntu session. This'll dump you back into Chrome OS.
You can always get back to the Ubuntu environment by typing "sudo startxfce4" in a shell again.
You can find more details about the crouton script for installing Ubuntu or Debian at github: https://github.com/dnschneid/crouton