Sketching in ZBrush for Designers - Free Chapter
Jose Cuahas released a free chapter from his Sketching in ZBrush for Designers tutorial.
NanoTile Textures for ZBrush
NanoTile Textures is an unofficial plugin that helps create tiling textures using NanoMeshes in ZBrush.
How to Paint Rocks in Photoshop
Marc Brunet shares a free video tutorial on how to paint rocks in Photoshop.