I've used the things as general hold-downs for things that I want to sit still on a ferromagnetic surface. I've used one to make a magnetic latch for a window screen. I've also used them as screw holders - pretty much any magnet will do for holding screws removed from some gadget you're taking apart, of course, but with a NIB magnet you just have to toss the screw vaguely near the magnet and it'll leap onto it.

You can use NIB magnets to hang tools from, as shown above, but they can work as an impromptu tool belt as well. Instead of dropping that pointy screwdriver into your pocket, where it'll do its best to make a hole in the lining and, subsequently, you, you can put a magnet in your pocket instead. Now, you can stick the screwdriver to the outside of your jeans. And it'll danged well stay there, too.

As will rather larger objects.

Use of mystic voodoo words and magic hand-movements as you adhere tools to your clothing may be called for, depending on the size and gullibility of your audience.

Those who appreciate bodily adornment can adhere a ferromagnetic bauble to their earlobe - or any other fairly thin body part - by putting a little NIB magnet on the other side. Use a couple of the big spheres on either side of your hand and you look like a very hard-core body modifier. Use big magnets on your ears and you will shortly look like an incompetent boxer.

There are, of course, lots of other experiments, simple and complex, you can try. Done with ferrite or alnico or simple steel magnets, they're underwhelming. Done with NIBs, they really work.

This is only scratching the surface of things that can be done with powerful magnets. If you want to make your own permanent magnet electric motor (which can be very simple) or alternator, neodymiums will make it work better than any other kind of magnet. Want to play with diamagnetic levitation? Can do. Do you prefer superconductor levitation? No problem.

And then there's art. You can make sculptures out of rare earth rod magnets and steel ball bearings; there's a toy that works this way, too.

And then there's magnetic braking.

Move a high-powered magnet around on a thick non-magnetic conductive surface - a slab of aluminium or copper, for instance - and you can easily feel magnetic braking at work. The stronger the magnet and the more metal there is (the base of a chunky CPU cooler is an excellent candidate for this experiment, and I've got a few of those kicking around...), the stronger the "syrupy" feeling you'll get. The magnet isn't attracted to or repelled from the surface, but it just doesn't want to move.

The reason this happens has to do with Lenz's Law. When the magnetic field around a conductor changes - because it's being moved past a magnet, for instance, or because a magnet is being moved past it - a current is induced in that conductor. This happens even if the conductor is just a chunk of metal that you're holding in your hand. Lenz's Law states that the current induced in a conductor by a changing magnetic field will flow such that it will produce its own magnetic field which opposes the original change in the external magnetic field.

So, basically, when a conductor moves relative to a magnet, the current induced in that conductor tries to stop it from moving. The bigger the field change - because of a stronger field, or faster movement - the stronger the braking force due to Lenz's Law will be.

I've got a piece of aluminium tubing with a half-inch outside diameter and a 3/8th inch bore, which happens to just neatly fit the little disc magnets from the ForceField grab bags.

The tube's 157cm long. Drop these disc magnets, or pretty much anything else, from a height of 157cm and they'll take about 0.57 seconds to hit the ground, thanks to the 9.8 metres per second per second acceleration of gravity.

A couple of the discs stuck together (to stop them tumbling) and dropped down the tube, though, take almost exactly 30 seconds to emerge from the other end. Magnetic braking.