Surprisingly enough, I do a lot of decorating for Halloween.
I used to be involved with a number of haunted house attractions and loved the kind of big, flashy props that those environments require. Electric chairs with flashing strobe lights and maniacs wielding roaring chainsaws are certainly effective, but as I've grown older I've developed an appreciation for a smaller, more intimate approach that places atmosphere and theatricality above cheap shocks. These days I'd much rather create props that are creepy and disquieting.
This particular project involves creating realistic parasitic worms for a "thing in a bottle" display. When finished, you'll have a reasonably realistic depiction of some of the (image warning) most gruesome real-life creatures in the world. Having a few preserved specimens on display should go a long way towards making your Halloween decorating memorable. Best of all, this is an amazingly cheap and easy project that can be finished in an hour or two.
To make our worms we'll be using liquid latex (Capitol brand latex carpet adhesive in this example, $3 at Home Depot), a glass cutting board, some off-white acrylic craft paint, and a cheap craft brush:
After cutting off the tip of the liquid latex squeeze out a line of the material on the glass sheet. Make sure you have good ventilation, since the ammonia in the latex reeks to high heaven.
A line about 6 inches long should be more than enough.
Now stipple the latex with the craft brush, spreading it out into a thin layer on the glass.
Once the latex is spread thin squeeze out a drop or two of the craft paint and stipple it on top of the latex. The stippling process not only mixes the paint in with the latex, but helps everything dry faster by increasing the surface area.
After about ten minutes the latex should be just slightly tacky to the touch. If it sticks to your finger when you tap it give it more time to dry. When it's fully dry use your fingertip to start rolling it up from one side by dragging your finger across the latex. It should come right off the glass and start forming a tube shape as it sticks to itself.
Once you have a good edge established you can use the length of your hand to continue rolling the edge over.
When you roll up the last of the latex from the glass sheet you'll have your parasitic worm.
The only thing worse than a thread-like worm devouring you from the inside out is a whole colony of worms turning your innards into a buffet, so make extras.
Ick! Now all you have to do is bottle 'em up. Congratulations, you're now on your way to having a display of specimens any mad scientist would be proud of.