Nexttut shows how you can model a simple lightbulb and shade it with Arnold.

This tutorial from NextTut shows off the ease and power of Arnold’s Layer shader to create a nice-looking lightbulb in Maya, complete with glowing filament. The tutorial shows how to use simple modeling tools in Maya to make the light bulb and the Arnold Layer shader to layer more than one shader together to nail down the final look.

Arnold has many layering nodes that range from layerRGBA, layerFloat, Mix, and of course, the layer shader.