Microsoft is announcing the launch of Windows 8 preview, for consumers. They’re doing this in Barcelona, near the Mobile World Conference (most likely on purpose). The preview will be made available today, for free, and will run on anything that ran Windows 7 as well as ARM devices (i.e. tablets).
The event is still underway so, as far as I can tell, there are no links to download just yet.
Update: The Windows team blog has been updated with full details and links.