NVIDIA has published a maintenance release of its PhysX SDK. You can download PhysX SDK 3.0.1 for PC, PS3, and Xbox from this page (an account is required).
NVIDIA has also published the PhysX SDK for Linux and Mac OS but only in version 3.0:
PhysX_3.0_SDK_OSX_BIN: Compiled using Xcode 3.2.4, 64 bit, on OSX 10.6.7.
PhysX-3.0_LINUX_64_Binary: This Ubuntu based distribution does not contain makefiles for the samples, but the sample source is complete.
The forum for PhysX SDK 3.0 is available HERE.