If you haven't gotten those grubby mits of yours on the Windows 8 Consumer Preview that was released just hours ago, hop to it! I'm downloading it right now, but I'm restricted to an 8Mbit connection, so it'll be just under an hour for me.
But, AMD have been kind enough to release some new drivers, dubbed the AMD Catalyst driver for the Windows 8 Consumer Preview. The driver set has full support for Windows 8's new WDDM 1.2 features. The rest of AMD's software features are also fully supported: Overdrive, CrossFire, and Eyefinity.
There is one downside, AMD Radeon 7000-series support, it's not included. These drivers don't support any of the GCN-based GPUs. Right now, AMD haven't even published a WHQL-certified Windows 7 driver for GCN, so we should see hopefully both of them, shortly.
Grab the drivers here.