I am recently working on opensource project called raspigcd.
This is the gcode interpreter that works on raspberry pi without any additional microcontroler. This post is just a teaser. When I will have more time, then I will write tutorial on how to use it.
The working version is at https://github.com/pantadeusz/raspigcd (also featured in hackaday.com - direct cnc control with the raspberry pi )
Right now I am working in TDD on next version with completely rewritten engine. The new approach will hopefully allow for faster movements and smooth acceleration control (also for laser engravers). It will replace current version. The new approach is called raspigcd2 and is in https://github.com/pantadeusz/raspigcd2 I intend to write post about it later on when it will be working smoothly on Raspberry Pi.