If you just got a bunch of cool LED's and you want to diffuse them (for various reasons) this is the instructable for you! Lots of LED's only come in those "waterclear" lens, not diffused. Diffusing makes the LED appear dimmer, but gives a wider viewing angle of the light. I recently bought color changing LEDs that only came in a non-diffused lens, that's when I made this instructable.
Step 1: supplies
The LED (duh)
fine sandpaper (I used 400 grit and ist worked great, but i haven't tested other sandpapers)
about 5 minutes of your life per LED