Skin shading is very simple using the Standard Surface shader in Arnold 5. From the Arnold user guide:

“When rendering skin, you would use a Radius color value like R:1.0, G:0.35, B:0.2, indicating that red should scatter deepest and green and blue less. This would replace the three layer workflow for skin where you would make the deep layer red to indicate that deep should scatter with a larger radius. Setting scatter_radius.R to a larger value would correspond to that.”

Below is a an example of such a skin shading setup (digital Emily files can be downloaded here).

Arvid Schneider has created a video that goes through the skin shading process:

Some fantastic examples of Bifrost by Igor Zanic, rendered with Arnold for Maya. Interview here.

Paolo Berto from Multiverse has some interesting tools to add complexity in Maya (with support for Arnold 5) that also includes using ABC data from Houdini (with velocity blur on varying topology). More videos here.

https://vimeo.com/219330616

Truca Team have an Arnold shader suite with over 256 shaders available for C4DtoA (using Arnold 5).

Greyscalegorilla have an Arnold playlist on Youtube. They are a useful resource even if you don’t use C4D.

There are now two versions of the Arnold User Guides. For example:

Arnold for Maya 4 User Guide

Arnold for Maya 5 User Guide

If you are not sure which version you are on, have a look at the top and it should say which version, for example: arnold for maya user guide 5

Also, the url for Arnold 5 has an A5 prefix, like so:

https://support.solidangle.com/display/A5AFMUG/Arnold+for+Maya+User+Guide

A tutorial that covers how to use the Flakes shader to create a glitter makeup effect can be found for the following plugins:

MtoA     MAXtoA     C4DtoA     HtoA

Here is a useful list of render farms that support Arnold.

John Paul Giancarlo has recorded an Autodesk webinar showing some tips and tricks in Arnold for Maya.

In this video, Chad Ashley from Greyscalegorilla demonstrates how to use the Curvature Map inside of Arnold for Cinema 4D (C4DtoA).

If you want to know how to fake a rounded corners shading effect, jump to the end of the video.