AMD has issued Catalyst drivers for the public beta version of Windows 8, you can download them over here. Interestingly, the Radeon HD 7000 desktop graphics card series isn't supported yet, users of these cards will have to wait a few more weeks for a driver fix.
Feature highlights of the AMD Catalyst™ driver for the Windows® 8 Consumer Preview:
Full WDDM 1.2
Native Stereo 3D support: Windows 8 will natively support Stereo 3D for full-screen and windowed gaming, and video applications
Unified Video API – Video playback is now integrated within the DirectX® 11 API; enabling simultaneous high quality Video and 3D content, and the potential for enhanced video transcoding performance
Optimized screen rotation
improved sleep / resume performance
Optimized Power Consumption
AMD Dual Graphics / AMD CrossFire™ Technology
AMD Catalyst Control Center / Vision Engine Control Center
Please note: A future AMD Catalyst Windows 8 driver release will add support for the AMD Radeon™ HD 7900 Series, and AMD Radeon HD 7700 Series in the coming weeks.