Although it is set to have a publicly available stable release during the second half of 2010, probably in a netbook, a version of it is already available for download via ZeroSec. Continued...
Instructions for running on VMware
1. Create a new Virtual Machine.
2. Select OS Linux/Ubuntu.
3. Create a blank hard drive (doesn’t matter what size since it is gonna be removed).
4. Extract the *.vmdk file to a folder.
5. Go to virtual machine properties and remove the hard drive created by the VMware wizard.
6. Add vmdk file as a new hard drive (in advanced options it should be IDE 0:0).
You can get Chrome OS version build by GDGT at the link above. You will need to create an account on their website in order to download VMware image. This build will require to login with your Google account credentials.
Download: The Pirate Bay
A torrent file of Chrome OS built on 11/19/2009. I recommend downloading this one since it has a local user account “mark” enabled (no password). All it does is allow you to login without a Google account. This is described in the build documentation. Shared user password (for sudo, etc is ‘chromeos’).
Catch a glimpse of the OS here.
Related: Google Chrome OS: Everything You Need to Know