ChanLum is a shader which takes a cheap shot at sub-surface scattering (SSS). It does this not by actually calculating the scattering itself, but by blurring and offsetting the lighting and (self)shadowing the object receives. With proper use, this produces results which look uncannily like the more 'professional' sub-surface scattering algorithms.
Since it's conception as a c.o.f.f.e.e. plugin for Cinema4D it's been getting ever more popular. It's not only used for it's SSS-looks, but also as an easy way to get other shading effects. Most of all, it's completely free.
As of today, the C++ version is available! A big thanks to David O'Reilly for the conversion! It's faster now, and supports light exclusion, as well as works with the new material system of C4D r8.5+. You can download the new version at the usual downloadlink below. The old c.o.f.f.e.e. version is also still available there.
ChanLum has been recently ported to LightWave by a good friend of mine, and reactions from the LightWave crowd have been quite positive.
Check the manual for an in-depth explanation and some examples (there is even a french version). For those interested, the initial page, describing how the shader came about, is still available.