There are a lot of nice things you can build from an old CD-ROM drive. Here is a magnetic stirrer! I made this one because I needed a really small one.
Step 1: Disassemble the Drive
Usually you need to open the tray before opening the case. You can use the casing for a lot of other nice projects. The magnet we are using is in the upper cover or on the motor which drives the CD.
Step 2: Removing the Stuff We Don't Need
Remove everything except the motor and the gears which drive the tray and cut on the dotted line. Then you need to glue the magnet on the last gear. I had to glue a piece from the white plastic thing between the magnet and the gear.
One can use the things that drive the laser to build a CNC machine and rumor has it that you can build a laser pointer and you can always try to scavenge the motor drivers.
Step 3: Add Power
Now you can attach the motor to a power supply, I used a cellphone adapter. You can put the volume control between motor and adapter to adjust the speed.
Step 4: Done!
Now we have got a nice and small magnetic stirrer. This is a picture of a different one with white gears. I used a lot of hot glue to secure all the loose wires. You can use a paperclip for a stirring bar if you want it really cheap.