Newton's cradles are purpose-built experiments that demonstrate the conservation of momentum and energy in bodies. They consist of five metal balls hanging in a line. When you pull back and release one of them, it knocks into the others and the ball at the other end is knocked away. This continues for quite some time due to the conservation of momentum.
The spinning coin experiment demonstrates the phenomenon of centripetal force. Find a balloon and insert a small coin into it. Blow the balloon up and tie the end. Now start swirling the balloon round to get the penny spinning inside it. It may bounce around at first but eventually it should settle down. When you have it swirling, stop moving the balloon and let the penny continue swirling on its own. It carries on for some time due to the low amount of friction acting on it. For an object to change direction it must have a force acting on it. In this case the force is a centripetal force -- the force provided by your hand to keep the balloon steady and keep the coin moving in a circular path.
Purpose-built experiments are available for cart collisions, which are really just metal blocks on tracks. These are made to collide with each other to demonstrate the difference between elastic and inelastic collisions. In elastic collisions (with a rubber block at the front of the cart), kinetic energy (energy due to motion) is not conserved, since both carts move off at slower speeds. In inelastic collisions, such as those for Newton's cradle, kinetic energy is conserved.
This last experiment demonstrates the action of gravity and air resistance on falling bodies. It is very simple. Take a feather and a hammer and release them to the ground. The feather should travel more slowly due to the greater air resistance in comparison to the gravitational force. Now compare this to videos of the same experiment conducted on the moon (available for viewing on YouTube; see Resources.) In this case the two objects dropped at the same speed, because there is no air resistance on the moon.