I had been planning to try out Google ChromeOS for a few days. Got to it finally. I used Virtual box to create a virtual machine to run the OS. The installation was painless. I had virtual box installed on my Ubuntu already. Here is a very nice blog that gives detailed description of how to go about it. Here is a link that gives a set of VM disk images for the OS. I used the vdi image. The whole process was simple except for a point where I got an error message and was prompted to recompile the Virtual Box kernel. Here is the command to do it : sudo /etc/init.d/vboxdrv setup
Here is another good blog on Chrome OS.