In the Spanish section there is a very nice thread about building a CNC machine, both the mechanical + the electronics and control SW.
Mechanical and a bit of electronics:http://arduino.cc/forum/index.php/topic,87714.0.html
The first few pages are a bit more about runting about the CNC, then it gets interesting with pictures and electronics.
A few demo videos of the developed electronics and some cool pictures.
SW to control the electronics described in the threads, well it can control most CNC electronics base on modern stepper drivers:https://bitbucket.org/fmalpartida/cnc-controller/downloads
The SW is nothing more than a gcode interpreter that executes gcode and converts them into stepper movements.