From Quirky Mind Stuff, by Richard Wiseman (via Matthew Cobb), we have a bunch of illusions, most of them amazing.
There are two that you can try yourself, but you'll need a friend. I tried them, and they both work for me, but for the "tightening thread" phenomenon, be sure that your fingers are relaxed and you're not trying to keep them apart.
That last illusion was too creepy
