Here is the setup in detail. All the pieces were built following directions from community projects. In this step I've included descriptions and links for all the hardware and software components for this project. If you follow all the instructions on all these links you will have a setup identical to mine. You can use whatever X-Y CNC platform you can get your hands on. I've listed some alternatives in one of the final steps.
From left to right.RepStrap
This is "McWire Cartesian Bot v1.2" - It is a version of Tom McGuire's CNC machine which has been adapted by The RepRap group for 3D printing. For simplicity, this Instructable is only using the X-Y axis. You should be able to use any X-Y stage that is driven with stepper motors.
If you would like to build this exact machine, detailed instructions can be found here (http://reprap.org/bin/view/Main/McWire_Cartesian_Bot_1_2) I believe these were posted by Zach Smith of the RepRap team.
Tom McGurie's original instructable is here (http://www.instructables.com/id/Easy-to-Build-Desk-Top-3-Axis-CNC-Milling-Machine/)
These driver boards are also the work of the RepRap team. They are "Stepper Motor Driver V1.2" Designed by Zach Hoeken. Full instructions can be found at http://reprap.org/bin/view/Main/Stepper_Motor_Driver_1_2.
These include ports for optical endstops. This is a very nice feature, but I am not using it here.
They have new version - Stepper Motor Driver v2.3 which is availble here (http://store.makerbot.com/featured-products/stepper-motor-driver-v2-3-kit.html).
SparkFun is stocking a good looking driver as well (http://www.sparkfun.com/commerce/product_info.php?products_id=9402).
The power to the drivers is from a desktop computer power supply. RepRap will also tell you how to do this!http://dev.www.reprap.org/bin/view/Main/PCPowerSupply
"Arduino with breakout"
This setup is using an Arduino Duemilanove with an Atmega 168 chip. Everything should work with other Arduino's and clones.
This breakout is also from RepRap. It is "Arduino Breakout v1.4" also Designed by Zach Hoeken. And available here. http://store.makerbot.com/electronics/pcbs/arduino-breakout-v1-4-pcb.html
Spark fun is stocking a nice screw sheild as well (http://www.sparkfun.com/commerce/product_info.php?products_id=9282)
"USB cable to PC"
The Arduino is connected to a desktop computer with a USB cable.
"Software on the PC"
I'm running an Ubunto distribution of Linux on my PC, the operating system shouldn't really matter since this project using Arduino and Processing software which is designed to run on most platforms (Linux, Mac, Windows).
If you don't already have them, You will need to load the Arduino and Processing software packages. http://www.arduino.cc/http://processing.org/