Yes! Finally, I got the “World – Volume” effect in Cycles rendering working, or at least I got it figured out. I am not going to go into detail on how I got it working, only that the Volume control in the World settings was moved, and the only way I could get the this effect to work was to add the Volume in the Node Editor. Sorry for all of you non-blender users, but this is a big deal. Here is a shot of what I managed to render today.
The whole idea of this effect is to add some visible, realistic, atmosphere in the Cycles Blender rendering engine so that you can see shadows being cast from off of objects though a misty, foggy in your scene. I had it sort of working in Blender 2.70, but since I upgraded to 2.71, just after it was released, the settings in the World Settings had changed. The shadowy effect only works with a spotlight source, I could not get it work with the Sun Light source, so I guess that is still in the development department over at Blender headquarters.
In the above scene, I used a spotlight, which is casting the shadow through the misty are, and a point-light, which does not cast any shadows in the volume setting, but you can see it in the fog. I am really excited about this effect becuase soon I want to render some scenes for next Halloween. This effect will be perfect to that eerie look and feel to my images.