Graphics artist Jorge Jimenez released an impressive real-time skin rendering demonstration which, as I mentioned before, does not fail to impress.
A video of the demonstration details the realism in the 'separable subsurface scattering' technology used in this realtime demonstration. It's best viewed in high definition.
Jimenez describes the technology as follows: "This movie shows my latest and final advances on real-time skin rendering (Separable Subsurface Scattering), which enables to quickly render skin in just two post-processing passes. Everything is rendered in real-time, from the skin to the film grain."
You can download the demo to try it out for yourself, but you'll need the equivalent of an nVidia 570 GTX to run it at optimal settings.