Chrome OS will only ship on specific hardware following deals struck between Google and the manufacturers. Chromium OS (the open source development version of Chrome OS) will be available as a disk image so that enthusiasts can put Chrome OS on any machine they please, though this won't get the same support from Google.
Since last year, Chrome notebooks from Acer and Samsung have been expected to arrive in the first half of 2011. A price point has not been finalized, though rumors say devices in the US will cost between $250 and $600.
Chrome OS differentiates itself from Android by targeting devices with physical keyboards. Google's thinking is that many people already spend all their time in a browser, and that building an OS that is essentially a browser will make computers faster, simpler, and more secure.