The long awaited but probably unplayable Crysis PC demo is coming out tomorrow. You can download it at the Nzone website (I would wait a day, the bandwidth hog could be humongous). And just in case you think your PC might meet the requirement, they have a helpful "test your system" button on the website so they can show you how sucky your PC really is :)
In case you forgot what this is, here is the official blurb:
"With mankind facing an alien cataclysm, your elite Delta force and North Korean forces combine, united by common humanity in a battle to save Earth. Graphically stunning, tactically challenging and always intensely immersive, Crysis sets player choice at the heart of its gameplay, with customisable tactical weaponry and adaptable armour allowing instant response to changing conditions. "