If the lights are still on in the banner above, keep looking! When all the codes are redeemed, the lights will go out and no more free candy.
Scour the website for product images with a ghost and a code. Once you find a code, go to "My Account" at the top of any page and then "Gift Certificates Send/Redeem" on the left and redeem that sucker as fast as you can!
If the code does not work, it has already been redeemed and you're too late. (We'll try to update them to "Redeemed" as soon as we can.)