Step 1: Materials
You will need:
-An old CD drive. I got one for a buck or so. It doesn't have to be fancy as long as it is tray loaded, not slot loaded. (You can't use the ones with hole you just put the CD straight into.)
-some thick wire, and also some thin one
-plank (length=length of the table; width=10cm or so; height=1 cm or so)
-cardboard, thick paper, rubber strap
-short metal straps, some more wood-we'll use it to mount the plank to the current desk
-normally off momentary push switches (I got mine from a VERY old keyboard)
-2x2AA batteries holder or 1x4AA batteries holder (not recommended, but exactly what I used).
drill (optional, but recommended)
Step 2: Disassembling the CD Drive
Take the CD drive apart. Just remove the case, the laser, 2 motors and stuff like that. In fact, you don't really need to disassemble that far. I did that because I'll use the other parts. But anyway, it is necessary to get to the wires of the round motor, as seen on images below.
Step 3: Extending the Desktop
First off, cut the aforementioned plank in three pieces. One will go left to the drive, one right to the drive and one will be 14 cm wide and I guess you could put it on top of the drive, but I replaced it with some much more lightweight cardboard. Using some additional wood, metal straps and wood screws, we'll mount the pieces of plank to the desktop itself. With help of thick wire and even more screws I put into the bottom side of the desk, I can easily make the CD drive stay in place.
Step 4: Making the Stash Itself
There is naturally not much free space between the table and the drive itself, but I figured out the gap is big enough for me to be able to put some pens there. So I made myself a paper holder for them. Using needle, I poke some holes evenly in a thick paper, then I pulled a rubber strap through them. I just made a knot on the other side of the paper to make sure the band doesn't come loose. I bent the very end of the paper 90 degrees and glued it to the tray using a poster clay. Yeah, I know. But it works. Just some wise words here: to make sure the paper doesn't stick anywhere during the opening/closing process of the tray, you want it to be LONGER than the drive itself, so that it slides on the rear end of the drive. This way it'll stay away from the variously shaped guts of it and it won't stuck that easily. (At least that's my experience talking; you may came across some differently shaped drive where you won't run into this problem.)
Step 5: Door
I placed the door on axis so that they open automatically once the drive slides up.The axis is made from a thick uninsulated wire that is secured with 2 wood screws that I put into the plank from bottom side. The door itself rotates freely along this wire with help of thin wire hanging loops, as seen on image. To prevent the door from being stuck every time the tray elevates, I had to "chew out" the middle part of it, but maybe you won't need to do that.
Step 6: Circuit
Generally speaking, there are 2 approaches to making the motor go both ways, when I don't count some fancy H-bridge or voltage-sinking-using electronic circuits.
1) Re-purpose a line car remote control.
2) Resemble the schematics on attached image like I did.
If you have a single 4 AA battery holder, just solder the middle wire in middle. The motor is the motor of the CD drive. You can easily connect it with the rest of the circuit just by plugging wires directly into the motor connector. I did the same thing, securing it with poster clay.
Remember: Whether you go for the first or second way of doing things, never press both buttons at the same time, as that would lead to a short circuit.
Step 7: Fine Polishing
I did none. But I might use some wallpaper along with some fancy metal stripes evenly distributed across the plank to mask the door... That's it for this tutorial, hope you enjoyed it!