UPDATE: 03:04EDT : This site — http://chromeos-cr48.blogspot.mx/2012/12/so-you-want-chrubuntu-on-external-drive.html — has info about how to install a bootable Linux for the Chromebook to a USB stick.
UPDATE: 02:30 EDT : This site has the same info as the OP, but is more readable: http://www.makeuseof.com/tag/install-linux-chromebook/
