Yes, Chromebooks run coreboot and almost every model has a community coreboot build with a SeaBIOS/EDK (UEFI) payload available. [1]
When you flash that, you lose the ability to boot ChromeOS, but you can install a standard Linux distro on them.
IMHO, Chromebooks are awesome machines. With ChromeOS they have one of the most secure boot chain/data models of anything currently shipping. Unlocked bootloader, vboot by default, all user data is encrypted, and power washing is trivial. Amazing battery life. Also, they're cheap, and guaranteed to run coreboot with a bootloader that can always be unlocked by the user.
