Had I found this site sooner, I would have told you about it. I may be the last person in the world to discover Instructables though. These ideas are great for a party with older kids or adults with a morbid sense of humor. Some of them may steal your appetite, but I guarantee guests won't be able to stop talking about your soiree for a while.
This one is my favorite. I stumbled across it this morning and it led to a lost half hour of browsing and wishing the kids still had their annual Halloween party.
These are kind of gross, but I'll bet tweens would love them.
Not as big of a gross out factor, but keeping with the theme.
Seriously sickening, and I don't know that the ingredients would be easily obtainable, but they would make an impact!