Free Brush Packs
Andrew Averkin has shared two brush packs for free, to be used with ZBrush, Quixel or Substance Painter.
ZSceneMgr for ZBrush
ZSceneMgr is a plugin for ZBrush that aims to improve your workflow with SubTools.
Nick Miller's ZBrush Tools
Nick Miller has created a collection of tools that automate, expand and add features to ZBrush.