OK, not exactly a quarter shrinker, but a quarter re-sizer; the quarter gets thicker as its diameter shrinks.
But what's wild about this is how it's done: by creating a massive magnetic field. From the site:
The quarter shrinker uses a high voltage capacitor bank and a triggered spark gap to apply up to 125,000 amps through a small work-coil of #10 AWG magnet wire which surrounds the coin. Once the spark gap is triggered, a current of over 1 million amperes in induced into the coin, and the interaction of the induced magnetic field and the field from the coil cause the coin to shrink radially-inward. At the same time, the work coil explodes into copper shrapnel, and then into a 8" ball of plasma. This all occurs in about 20 millionths of a second. The experiment is done under a bulletproof Lexan blast shield. It's a very energetic and dangerous process - don't try this at home folks... :^)
The guy also has a huge tesla coil and a lot of really wild images featuring that. Here's his page (with images that load pretty slow):
http://navarrone.com/tesla/tesla4.html