Chromium OS is the new OS that is the root of Google Chrome OS.
In these days Samsung and Acer dropped out two "Chromebook", -netbooks- that run Chrome OS.
These Chromebooks have online application so they need continue internet connection to work.
For me they are a bit limited, but for their use they work great.
You can download and install (better in a virtual machine) Chromium OS:
http://chromeos.hexxeh.net/vanilla.php