makehumancommunity.org

For those who didn't know - you can get early/offshoot blender builds at http://graphicall.org/
(The principled/disney shader has been available here for a few months now, currently under 2.78.5)

(the principled shader is awesome and you should try it)

There are also official daily builds here: https://builder.blender.org/download/

And this late in the development cycle, there is also a beta ("test build") for the next release at https://download.blender.org/release/Blender2.79/