As an experienced Ubuntu user and Linux enthusiast, I've tested Google's lightweight ChromeOS—essentially the Chrome browser powered by web apps—without buying hardware like the $249 Samsung Chromebook. Here's how you can try it alongside Ubuntu, or even make it your daily driver.
Important Note: This Chromium OS package requires 64-bit Ubuntu.
1. Download the lightdm-login-chromiumos_1.0_amd64.deb file, a modified version enabling direct LightDM access.
2. Double-click the .deb to install via Ubuntu Software Center.
Or via terminal:
wget https://github.com/downloads/dz0ny/lightdm-login-chromeos/lightdm-login-chromiumos_1.0_amd64.deb
sudo dpkg -i lightdm-login-chromiumos_1.0_amd64.debLog out, then select "Chromium OS" on the LightDM screen.

Enter your Google password to log in.

First time? Follow the "Getting Started Guide" for printing, offline access, files, wallpaper, and more.

Use it like Chrome: browse, tabs, apps. Controls: bottom-left for new tabs/Web Store; bottom-right tray for Bluetooth, Wi-Fi, volume. Note: "Stop" logs out to LightDM only.

From developer info and my hands-on tests:
Works:
Doesn't Work Yet:
Many issues are in progress. Test it to match your needs—uninstall easily if not.