Science toys. Easy to make Railguns and other science toys.

Capt'n Midnight

http://sci-toys.com/index.html - Perfect for the budding evil genius bent on world domination.

Magnetism:
Magnetorheological fluids
A magnet in mid-air
Pyrolytic graphite in mid-air
The Gauss Rifle: A Magnetic Linear Accelerator
A Curie-effect heat engine
A Magnetic Ring Launcher

Electromagnetism:
An electric motor in 10 minutes
Fun with High Voltage
A 10 minute railgun
A 30 second motor

Electrochemistry:
A plastic hydrogen bomb
Building your own solar battery.
Building a Hydrogen Fuel Cell.

Radio:
A quick and simple radio
Building a radio in 10 minutes
Build a portable crystal radio
A radio out of household items
A simple AM transmitter
The Three-Penny Radio

Thermodynamics:
Simple heat engines
World's simplest steam boat
A simple rocket engine
A Film Can Cannon
A metal that melts in hot water
A room temperature liquid metal alloy
A simple solar powered heat engine
Homemade Ice Cream

Aerodynamics:
A Bernoulli levitation ball
A Homemade Vacuum Pump
A Classic Propellor Toy

Light and optics:
Simple laser communicator
Make a spectroscope from a CD.
Making permanent rainbows.
The impossible kaleidoscope
Make your own 3D pictures
Make a solar hotdog cooker
A solar powered marshmallow roaster

Biology:
Photography through the microscope
Video through the microscope
Listening to Electric Fish
Using a video camera as a microscope

Mathematics:
Kaleidocycles
A Geodesic Dome

Computers and Electronics:
A Computer Controlled Transmitter
A Free Space Laser Data Transmitter
Fun with Solderless Breadboards
A Digital Thermometer
A Simple 1 Watt Amplifier