You can get the kit for this project from the MAKE store. The kit isn't required, but makes acquiring the materials a breeze.
Step 1: Care and Feeding
The rare earth magnets used in this project are an alloy of Neodymium, Iron, and Boron (NdFeB). They are very strong, capable of affecting each other from more than 18 inches, but not indestructible. Their protective nickel plating can chip and break through repeated impact, sending fragments flying. Do not machine, drill, heat, or ingest these magnets.
Keep these magnets at least a foot away from all magnetic media, including computers, hard drives, floppy disks, cassette tapes, VHS tapes, and credit cards. Keep them away from consumer electronics, including computer monitors, VCR's, TV's, cameras, cellphones, and personal music devices. Keep them away from things you don't want magnetized, like watches and tools. Keep them away from people with pacemakers or other implants.
Bear in mind that magnets will jump to each other (or anything ferrous) if given a chance. It's better to stick a magnet on something large and stable to keep it out of trouble than to let it wander around.
These magnets are for use by responsible adults, keep them away from infants and children. Handle with care to avoid being pinched. End of lecture, have fun.