1 pack of Raspberry Jello
2 packs of Gelatin
Play-Doh (for the mold)
A Lego guy (also for the mold)
A little squirter thing to fill the mold
Non-stick cooking spray
Water (or Kool-Aid if you're adventurous)
Other ideas include lime zombies, orange pumpkins (taste about as good as real pumpkins), or pineapple ghosts. Ghosts taste like pineapples if you didn't know.
The only things I had to pay for was the Jello, gelatin, Play-Doh, and some Legos. All in all, it was about $20.