A magnetorheological fluid is a liquid that hardens near a magnet, and becomes liquid again when you remove the magnet. They are simple to make in your kitchen after a trip to a sandbox.
http://sci-toys.com/scitoys/scitoys/magnets/magnets.html#rheological
This very simple toy uses a magnetic chain reaction to launch a steel marble at a target at high speed. The toy is very simple to build, going together in minutes, and is very simple to understand and explain, and yet fascinating to watch and to use.
http://sci-toys.com/scitoys/scitoys/magnets/gauss.html
The beads all repel one another, and arrange themselves in a way that clearly shows the effect of gravity -- the beads at the bottom are closer together than the ones at the top, forming a beautiful mathematical progression.
http://sci-toys.com/scitoys/scitoys/magnets/ring_launcher/ring_launcher.html
The motor is simply a battery, a magnet, and a small coil of wire you make yourself. There is a secret to making it (which I will of course share with you) which is at the same time clever and delightfully simple.
http://sci-toys.com/scitoys/scitoys/electro/electro.html#motor
Investigate the performance of batteries in a scientifically valid way.
http://www.sciencebuddies.com/mentoring/project_ideas/Elec_p008.shtml
Which battery lasts the longest out of four different brands, Duracell, Energizer, Eveready and Rayovac?
http://www.energyquest.ca.gov/projects/battery.html
In this experiment, students will make observations of a coupled oscillator.
http://www.pasco.com/experiments/physics/may_2003/home.html
An easy attractive project make an electromagnet using a nail and some battery.
http://www.energyquest.ca.gov/projects/electromagnet.html
It is fairly easy to build an electromagnet. All you need to do is wrap some insulated copper wire around an iron core.
http://education.jlab.org/qa/electromagnet.html
Students will use a Magnetic Field Sensor to discover the characteristics of fields around magnetized materials.
http://www.pasco.com/experiments/physics/april_2002/home.html