David Richardson has created a multiple-part tutorial for modeling a mech in ZBrush.
Character Pipeline for Games R2
Check out Kurt Papstein's new program for Phoenix Atelier, Character Pipeline for Games.
2 New ZBrush Character Production DVD Releases by Michael Pavlovich
Eat 3D have released two new ZBrush character production DVDs by Michael Pavlovich.
ZBrush SIGGRAPH 2013 Recap
Here is a massive recap of ZBrush's presentations from Siggraph 2013.