Steven Dufresne at Hackaday has a great piece up on the history of the capacitor:
“The history of capacitors starts in the pioneering days of electricity. I liken it to the pioneering days of aviation when you made your own planes out of wood and canvas and struggled to leap into the air, not understanding enough about aerodynamics to know how to stay there. Electricity had a similar period. At the time of the discovery of the capacitor our understanding was so primitive that electricity was thought to be a fluid and that it came in two forms, vitreous electricity and resinous electricity. As you’ll see below, it was during the capacitor’s early years that all this changed.”
The piece includes some great do-it-yourself ideas. Read: History of the Capacitor – The Pioneering Years.