PiXELS:3D is a powerful and affordable 3D program for MacOS X by Pixels Digital.
Here's my attempt at creating a decent subsurface scattering effect in Pixels:3D. It is based on the technique presented by Pixar at the Siggraph RenderMan course 2003 "Shading a coral reef". Enjoy.
The Pixels web page will tell you lots of reasons why you should want their program over other programs. I don't want to repeat that but will tell you why I chose Pixels over other programs:
Pixels:3D is the only program I know of that does not only ship with a somewhat RenderMan compliant REYES renderer but does fully rely on RIB files to talk to its renderer. This will not only allow you to render RIB files from other programs in the Tempest renderer that's included in the Pixels package but you can also easily render the scenes you made in Pixels in other RenderMan compliant renderers like Pixar's PRMan, 3Delight or Aqsis. Furthermore, you are free to modify the RIB files before rendering them or better have a script that modifies them for your needs. I don't know of any other program in that price range that would allow you to customize your workflow this good - when you use Carrara, TrueSpace, Real3D or Cinema4D you are more or less restricted to the renderer the respective program ships with and you especially cannot add your extra steps between the app and the renderer.