Well Andrew Price with Blender Guru Has given us a sneak peak at his nature academy series. The full thing will be coming out in a couple of weeks depending on when you read this post.
(http://thenatureacademy.blenderguru.com/sq/5796-snowy-mountain-tutorial) is the link to his tut on making snowy mountains.
Nice trick from Andy Goralzck for getting the slope!
I too have tried 101 different ways to get this in BI (including normal nodes (which are in view space so they don’t work), baking a world space normal map and using the blue channel …(needslarge res texture and doesn’t update as you go) writing a script to bake vertex colours (only works at base mesh resolution) even duplicating the geometry and offsetting it (poly hungry!)
Andy’s trick is great! (even fourth hand!)
He should’ve made 3d trees and composited them in behind him as he talks.