Master dDo for Photoshop with this complete overview by Wiktor Ohman.
Free Photoshop Brushes
Several professional artists have made available their Photoshop brushes for free.
You Found Me - Timelapse
Check out this timelapse of Cezar Brandao's recent sculpting livestream.
Cyborg Design - Concept Art Production Techniques
Instructor Michael Pedro gives a detailed overview on concept art production techniques in ZBrush and Photoshop.