Master dDo for Photoshop with this complete overview by Wiktor Ohman.
Quixel’s immensely popular NDO and DDO have been reimagined, and along with 3DO and MEGASCANS are part of the upcoming Quixel Suite.
Gnomon - Design Techniques for 3D Concept Art
The Gnomon Workshop present Design Techniques for 3D Concept Art, a DVD tutorial by Gavriil Klimov.
Art for Games - Memory Folds in Clothing Tutorial
Art for Games have posted a free tutorial on creating memory folds in cloth, using ZBrush and Photosohp.