I found this interesting set of photos through www.makezine.com. They show the 'skeleton' of a movable tentacle.
While the design is a bit elaborate, and there aren't any instructions, it might give you some ideas on how to make a slithering tentacle prop for Halloween. Personally, I would love to have something like this sticking out of my mailbox!
Check out this, um, disturbing t-shirt from despair.com.
Give you some ideas for a Haunted Forest? :)
I just thought is was a cool idea. But if you want to buy the shirt, it's a limited offer. So act quickly! Go here http://www.despair.com/cuforhoch.html
Available in "He loves me not" for you disturbed ladies out there too (You know we love you... right?).
For your mad-scientist lab, try out these 2 x-ray sets from American Science and Surplus (original manufacturer is Roylco)
These are actual x-rays reproduced on transparencies for 'educational' purposes. But there's no reason you couldn't use them for your Halloween display!
Here's a thought: Cut out silhouettes of random objects (scissors, railroad spikes, Barbie ™ dolls) and tape them behind the chest x-ray to ‘implant’ them in your victim.
Or combine x-rays make a zombie with a 'hand' inside! Or combine images from the human and animal sets. What might a mutant killer frog eat?
While you are there, take a look at the wonderful paper masks, games, coffins, haunted houses, and other fun paper toys. I've made several of these and they are a blast!