NVIDIA released GeForce 177.39 beta drivers - these are the ones that have support for PhysX. Here's the changelog:
Adds support for GeForce 9800 GTX GPUs.
Adds support for NVIDIA
PhysX Technology for GPU PhysX hardware acceleration on GeForce 9800
GTX, GeForce GTX 280, and GeForce GTX 260 GPUs. The GeForce v177.39 driver
package includes NVIDIA PhysX System Software v8.06.12. The Unreal
Tournament 3 PhysX Mod Pack can be downloaded here.
Supports single GPU and NVIDIA SLI technology on DirectX 9 and OpenGL.