Recently, we posted about a subsurface scattering node that was being developed. Well the good news is that its now integrated into the internal renderer and will be part of the 2.44 release.
Quoted from the blender website:
Subsurface scattering is a new material option to render materials like skin, marble or milk. For these materials light rays are not always reflected at the surface, but can also scatter under the surface and leave at another position. This leads to a softer appearance, as light is blurred out over the surface.
Blender uses a method to simulate this effect for diffuse illumination, in a two step process by rendering a lightmap in advance.
Some amazing results can be achieved with the effect like this tomato render by Enrico Cerica: