This basically comes from a small project I decided to do after fitting a new shelf and realising that there was little to no light underneath it, so in order to provide some light, and to make it look cool (it ties in with the theme of my PC) I thought I'd use some left over parts to make some cool undershelf lights.
I found out last night that my PC doesn't turn it's USB off when it's shut down, so I've added a switch and a capacitor (for a fade effect), there is a circuit diagram on the making stage.
Step 1: Collect Your Parts! (..and Tools)
You will need:
2x 3mm Blue LEDs (High brightness or normal, it's up to you)
1x 56ohm resistor
A male USB connetion
a length of cable.
Now, this is better if you have a PC, laptop or anything with a USB connection nearby, but you could do my inctructable on making a battery operated 5v power supply (https://www.instructables.com/id/Simple-5v-PSU-battery-powered/) and then combine it with this to make your undershelf lighting.
Step 2: Make It
Follow the circuit diagram to build it. (The capacitor and switch are OPTIONAL, but reccomended)
Step 3: Fit It.
Now, this step will vary from shelf to shelf, so I will leave it to you to figure out how you plan to mount it (tape if you're really cheap...). I had a gap behind my shelf, so I slotted them down there.
Step 4: Admire.
Stand back and admire your work.
Looks great doesn't it?