The Van de Graaff generator is a device capable of accumulating large quantities of charge upon a highly insulated terminal. The accumulated charge may be either positive or negative. Probably a more impressive demonstration than the Winshurst machine.
Try putting stacked pie plates on top. The charge is concentrated in the outermost, i.e. top, plate, which is repelled from the generator. As each builds up charge, it flies off.
You can also do neat stuff with soap bubbles or with simulated "hair" on top of the generator.
Click here for movie (1.0M mpeg).