A high performance CNC controller...
An Arduino shield for the grbl CNC controller software.
The very popular Shapeoko CNC system being powered by TinyG.
grblShield is a shield that plugs onto the Arduino development platform transforming it into a CNC controller using the grbl CNC firmware
TinyG is a high performance USB based CNC 6 Axis controller supporting XYZ linear and ABC rotary axes with 4 motor outputs.