An open source, embedded, high performance g-code-parser and CNC milling controller written in optimized C that will run on a straight Arduino

Other

grbl

A GCode sender (not only for lasers or plotters) for up to two GRBL controller. SVG, DXF, HPGL import. 6 axis DRO. 

A web-based interface for CNC milling controller running Grbl, Marlin, Smoothieware, or TinyG.

A cross-platform G-Code sender for GRBL, Smoothieware, TinyG and G2core.