The Wimhurst type of generator consists of two circular plastic plates, which rotate in opposite directions by a hand-cranked belt drive mechanism. On each disc are pieces of metal foil, which both generate and carry small charges of electricity. Brushes on the front and back distribute the charges to a Leyden Jar, which stores the charge like a modern capacitor.
As the plastic discs revolve, a high voltage spark will jump between the electrodes when they are brought close together. Cool!
Here is the Wimshurst Electrostatic Generator available at Edmund Scientifics.
If you would rather build your own Wimshurst generator you will want the book: Homemade Lightning: Creative Experiments in Electricity.