CrossOver is a nifty program that allows you to run Windows programs in OS X and Linux. And because of some promotion having to do with the price of gas (don't question it), all CrossOver products (including CrossOver Games) are free today and today only. All of the traffic has brought the site to its knees, but you can still download the software and request a serial number. Just make sure to actually register your software by tomorrow or the offer might have disappeared. [CodeWeavers via Digg]