Small magnets are both fun and useful. You can do a variety of tricks that display the magnets' properties while also putting on a cool show. Or, you can apply their unique properties for useful purposes, such as getting batteries out of electronic devices or picking up staples or straight pins.
Put a wooden dowel or other non-conductive material through several doughnut-shaped magnets. Make sure that one is facing a different way from the other magnets. Affix a piece of cardboard or wood at either end of the dowel. When you stand the dowel on end, some of the magnets will float, because they will be repelling one another.
Laptops often trigger their sleep function through a magnet in the screen. When you close the screen, two magnets connect, telling the laptop to go to sleep. You can trick your laptop into going into sleep mode with the screen open by putting a magnet at the point where the screen makes contact with the laptop when closed. This is fun, but be very careful. If you put the magnet near the laptop's hard drive or screen, you can ruin them.
Floating Paper Clip
Place a small magnet so that it is hanging off a desk or table. Tape a piece of string to a paper clip and tape one end to the desk. Hold the paper clip near the magnet and slowly move it away until the clip appears to levitate. Once you find the right distance, the paper clip will float because it is attracted to the magnet but cannot break free from the string and tape. This is a fun way to show how magnets can move objects using their magnetic energy.
Put a piece of string in between a couple of magnets. The magnets will stick together on either side of the string, holding themselves to it. Dangle the string from your hand, and the magnets will point north. This instant compass is fun for impromptu navigation.