Magnetism is a force that attracts and repels things. It is the result of the movement of charged particles. Although the theoretical concept may sound difficult, it is easy to demonstrate to even young children with very simple experiments. Nickel and iron are two metals easily effected by magnetic forces (they are attracted to magnets) while copper and aluminum are not (and can not be magnetized.)
Electrical engineer Rick Hoadley (a.k.a. Cool Magnet Man) shares his magnetic enthusiasm with this virtual textbook and dozens of experiments that you can either buy or build. "Some of the experiments are very basic - things you've done since second grade. Others are unique; perhaps you hadn't thought of doing some of these before, or had difficulty in trying to set them up." Chapters that include experiments are marked with a yellow "Expt" button.
Exploratorium Snacks are not the kind you eat after school, but rather experiments you can do at home or in a classroom. This collection includes a dozen Magnetism Snacks arranged in alphabetic order from Circles of Magnetism (use a 6-volt lantern battery to create a magnetic field stronger than the earth's) to Stripped Down Motor (an electromagnetic coil of wire spins when it interacts with a permanent magnet.) More science snacks, such as chemistry, color, and sound experiments, can be found on the Snacks by Subject page.
"Magnetic fields are produced by electric currents, which can be macroscopic currents in wires, or microscopic currents associated with electrons in atomic orbits." This illustrated chapter from the Hyper Physics textbook (hosted by physics department at Georgia State University) explains magnetic fields for high-school and college students. Unlike a linear printed textbook, however, there are lots of links to help you explore related concepts.
Walter H. G. Lewin received his Ph.D. in Nuclear Physics in 1965 from the Technical University of Delft, and has been an MIT physics professor since 1966. This video lecture "for learners young and old" runs an hour and forty-two minutes, and is part of the Family Adventures in Science and Technology at the MIT Museum. "Lewin is at his electrifying best when working with children from the audience. He gives a 12-year-old girl the worst hair day of her life, and offers a young boy 10 cents for 10 hours of backbreaking labor."
Developed for science students in middle and high-school, this online textbook includes dozens of virtual experiments demonstrated with animated video, and discussion questions for classroom or home school. For example, one of the first animated experiments allows you to cut a magnet in half (by dragging scissors over a magnet) and seeing what happens to the magnet's poles. "What is happening when you cut the magnet? How small do you think you can make a magnet before it no longer acts like a magnet?"