Here is a video from the workshop I gave at De Montfort University, Leicester as part of the Future of Sound tour.
http://www.futureofsound.org/31.htm
It was on DIY synth building using a CMOS 4093 chip, a few pots and ldrs, some capacitors and a breadboard.
The most expensive thing you have to buy to make this is the breadboard.
I also performed on the Wednesday evening.