GELATIN STALAGMITES experiment

Procedure
Pour a small pile of unflavored gelatin on the tabletop or plate.
Rub a balloon in your hair and bring it near the gelatin.

Explanation
The particles of gelatin will arrange themselves in columns resembling stalagmites as the charged balloon is brought near. The gelatin particles are normally neutral, but become temporarily polar when brought near the balloon. The negatively charged balloon repels the negative charges and brings the positive charges closer to the surface of the gelatin particles. The polarity is transmitted to the neighboring particles, until you eventually have a long chain of molecules held together by the attraction of opposite charges.