For more information on magnets, try these books:
Playing With Magnets, by Gary Gibson (Aladdin Books, 1995). This introductory book is good for third-to-fifth-graders. It contains a few simple experiments.
These next three are better for fourth-to-sixth-graders. They are listed in order from easiest to hardest:
The Science Book of Magnets, by Neil Ardley (Harcourt Brace Jovanovich, 1991)
Magnets, by Steve Parker (Gareth Stevens, 1998)
Experimenting with Magnets, by Alan Ward (Chelsea House, 1991).
For junior-high kids, try:
Science Projects about Electricity and Magnets, by Robert Gardner (Enslow, 1994). The projects described here are more challenging.
Here's a Web site for kids that tells about magnets and lists some experiments (making a compass, an electromagnet). www.stmarys.vic.edu.au/research/magnets/index.htm
From here you can also link to the 'Bill Nye, the Science Guy' site with lots more on magnets and other stuff.