Here is the smallest USB LED you've probably ever seen! It uses a USB plug made with a piece of perfboard, so you should already have everything needed to make this. No cutting up USB cables here!
This kind of homemade USB plug could also be used for other things, like repairing USB cables.
Step 1: Supplies
All you need for this project is:
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.