I know many others have submitted instructables detailing how to make an LED writer pretty easily but I thought I'd show some of you who may be just as lazy as I, how to make one in under two minutes with materials you're sure to find around the house.
Step 1: Materials
All you need is:
a 3v button cell battery (cr2302)
about a 2 inch strip of wire
tape (vinyl insulating tape works best)
Step 2: Attach the LED
Tape the negative lead of the LED (the shorter side) to the negative side of the battery. Make sure that the positive lead is insulated from the positive side of the battery.
Step 3: Bend and Attach the Wire
Strip the wire completely. Bend the wire to give a relatively large contact patch for the switch. Ensure that you leave about an inch or so un-bent.
Tape the wire so that the un-bent portion touches the positive lead of the LED and the bent part hovers just over the slimest part of the battery.
Step 4: Fine Tune and Test
Now just fine tune the bend in the wire to ensure that when your not pressing on it the wire is not touching the top of the battery. The idea is that when you press down on the wire it completes the circuit, connecting the positive lead of the LED to the battery.
At first I thought this design would only be temporary and would only work for maybe an hour max before I would have to completely remake it but I actually found it to be surprisingly robust. Of course if you have a a two pin push button those are a little better.
You may be able to make the design even more sturdy by hot gluing or soldering the wires together but, of course, this makes it a little more complicated.
Now go out there and have fun drawing with light.