This kind of homemade USB plug could also be used for other things, like repairing USB cables.
Step 1: Supplies
A Soldering Iron
150-200 Grit Sandpaper
Blue LED (Other colors will work just fine, too)
Small Piece of Perfboard
I used a 1k resistor because I just wanted a nice looking light, not a blinding one. ;P Feel free to use a different value if you choose.
Step 2: Score and Sand
If your piece of perfboard isn't already in a strip like mine, cut some out by scoring the perfboard with your X-Acto knife, then breaking it apart.
Take your strip of perfboard and score it four traces in with your X-Acto knife (Four USB pins = Four traces). Break the piece off so you have a squarish piece that fits in a USB port. If it does not fit right, sand it a little bit to make it the right size.
Step 3: Bend and Cut
Bend the positive lead of the LED 90 degrees out, and bend one of the leads on the resistor down and out, so it will line up with the bent LED lead. Check the pictures if you're a little unclear on what to do; after all, they ARE worth a thousand words each.
Clip the leads down so that there will be enough left for soldering, but clip them enough so that they will not get in the way of anything. Make sure everything lines up with the two outer traces on your perfboard, like in the second picture.
Step 4: Put It Together
First, you need to fill the perfboard traces with solder. This is where bridging actually comes in handy. :P
You only need to do the two outer pins, but later I did all four for good looks.
Next, solder the LED and resistor together.
Solder the LED/Resistor combo to the perfboard. Make sure you get the polarity right. In the pictures below, the negative side of the LED needs to be on the left side, not the right. Make sure you don't mess that up, or your USB LED won't light.
Step 5: Plug It In, Plug It In
It might be a good idea to sand the contacts after soldering, to remove oxidization and make it look nicer.
Plug it in, and watch it glow! These are easy to make, and very small, so many of them could fit in a pocket at once! I've made several for some of my friends and teachers. :) These are good for using unused USB ports, and they look cool, too! Have fun. ;)