Get this inexpensive version that makes big sparks!
from Engine DIY: BUY NOW: Wimshurst Electrostatic Generator
Wimshurst Electrostatic Generator: this device uses two counter rotating disks of metal pads to separate charge via induction. The repulsion felt by electrons as the triangle plates pass by each other pushes charge to flow across two conducting rods, one on each side, which allows the charge to stack up. This excess charge is then stored in old fashioned cylindrical capacitors (Leyden Jars) until the resulting 30,000+ Volts is achieved to jump the air gap. This device goes back to 1883- invented by James Wimshurst
This inexpensive electrophorus set works great!
From eBay: BUY NOW Electrophorus Demonstration Set
The container is just the middle part cut from a plastic water bottle, and the "hail" stones are Styrofoam craft beads:
From Amazon: BUY NOW Styrofoam Craft Beads
For Volta's Hailstorm to work, the beads must be coated with a conducting spray (here is what I used):
From Amazon: BUY NOW Staticide Spray
Wikipedia has a very nice description of the physics of the Electrophorus and how it is used to transfer electric charge.
Volta’s Hailstorm and Electrophorus: electrical forces due to electrostatic charge send foam beads flying in this version of the historic demonstration by physicist Alessandro Volta. The beads are covered with an electrically conductive coating allowing them to transfer charge from the environment to the plate of the electrophorus. The acrylic platform becomes negatively charged when rubbed with a paper napkin, but it is also an insulator so the charge on it can not flow on to the aluminum plate of the electrophorus. Instead the charge on the platform pushes electrons to the top of the plate (like signs repel) and touching the plate results in a spark that removes the electrons giving the plate a significant positive charge that will then attract the beads.