Step 1: Parts needed
-62ish OHM resistor***
-LED of your choice
-Old USB plug
-Twisted wire or hookup cable
-Relatively stiff wire (doesn't have to conduct electricity)
-Some tape (electrical is probably the best)
***Resistor may vary depending on your LED needs. Source voltage is about 5 volts from USB. I suggest this website if you don't want to second guess yourself: http://led.linear1.org/1led.wiz. I use it all the time because I doubt my math abilities.
Step 2: Cutting
Pro Tip: Don't use a USB plug with shielding like I had. It makes it far more annoying to cut up with shielding.
After you hack up the USB plug, find the positive and negative wires. Don't assume that red is positive and black is negative. Never assume in electronics. In my case, yes red was + and black was - :). But I checked and that's what counts. Cut the other wires if any, you just need power.