I've been building a CNC Mill, and I wanted it to be Arduino controlled so that I can tailor it to my needs. I took a version of the RepRap firmware created by Chris Meighan and used by Contraptor that has arcs and acceleration, and I expanded it so that it can draw arcs in all three planes. I've also added manual controls for an external joystick as well as some bug fixes. I am kind of new to the Arduino platform, and my modifications might not be the most efficient. I'm still trying to work out all the bugs. This version works with any stepper driver that takes two wires for step and direction (297L). If anyone is interested in trying it out on their machine (RepRap or CNC Mill), you can get it here: Arduino CNC Mill/Laser Cutter/Extruder download | SourceForge.net
If you do try it out, please report back how it went. I'm open to all suggestions on how to make the code better. You can read a more in depth description of the firmware here: Contraptor Firmware With XY, XZ, & YZ arcs - Contraptor