Edge nodes takes the normal and z-pass, along with alpha and ob/mat indexes, and utilizes the already available filters within Blender's composite node system-- Sobel, Laplace, etc.
This is not to replace Blender's own "Edge" or the Freestyle branch by any means, just to give more options and compliment what already exists for line art.
Please do experiment and abuse this setup, and please improve on it!
This has been a collaborative venture between LightBWK, Daniel Kreuter, and myself. A post on how it works is here: http://www.blenderNPR.org/bnpr-exclusive-edge-nodes-part-3/