A little CNC controlled Pen Plotter I made from two old CD drives.

It is pretty fun and easy to control CD drives stepper motors from the Arduino. You will need stepper driver boards (if you do not want to solder your own circuit). I found these ones from Aliexpress:
http://www.aliexpress.com/item/free-shipping-5pcs-lot-L298N-motor-driver-board-module-for-arduino-stepper-motor-smart-car/1613798843.html
You can use the Servo and Stepper library to make coding easier. This is not meant to be a complete description of the project but rather an inspiration if you want to hack together your own.
The first thing you need to do is to take out the guts of two old CD drives and mount one on top of the other at 90 degrees. I used Meccano for that.
Strip the drives from the electronics and optic parts you do not need.Then print out the parts for the adjustable table and the pen lifter and super glue them where the CD laser used to be mounted.
For the pen lifter, you will need a small 9g mini Servo:
http://www.aliexpress.com/item/Free-Shipping-5X-SG90-9g-Mini-Micro-Servo-for-RC-for-RC-250-450-Helicopter-Airplane/1131556973.html
I had to sand paper the sides of the slide to make it fit and use the Dremel to cut the slot a bit wider. The pen I use is 9 mm in diameter.
OK, this was somewhat short but if you want more info on how to wire this thing up, let me know.
See http://youtu.be/-EqaYc7K-nY for a video of the machine in action.