Any old LED will work, but it will be a lot brighter if you can find some 5mm white ones. Pretty much all LEDs will run happily (and forever) on the low current supplied by a tape/CD player motor.
What makes this project really cool is that the end result is not just a demonstration of free power generation, it's also quite practical. The LED is blinding bright... I always keep one handy in case of a thermonuclear exchange induced power outage.
Here's a video. It was kinda hard to take a video while spinning it...Oh, and I find it easier to spin it towards me (more leverage or something).
Step 1: Here's what you will need
1. Small Electric motor from a CD player or Tape player. Larger motors will work WAY better, but tiny motors are easier to find in the junk pile.
2. Any LED. 5mm white ones are preferred because of the brightness, but little green or red indicator LEDs will work fine too.
3. It's totaly optional, but pliers would probably help a little.
Step 2: LED installation
LEDs only work one way (light emitting DIODE), so if it wont light up, switch around the LEDs leads and try again.