As I just posted in Francissimo's thread, I thought I put two links here. First one is an automated texture shading method to create relief shading enhanced with a "rocky" feel. The tool is tweakable so I advise you to make some tests first to get a hold on it. This is aimed at people who have a bit of GIS practice as you'll need to use floating-point raster as input and be careful with the data you'll use.

http://www.textureshading.com/Home.html

An other link to a cool website probably already mentionned previously here because it's, according to me, a mut-see. It provides some really interesting tutorials mostly aimed on the creation of relief and its enhancement.

http://www.shadedrelief.com/shadedrelieftuto.html