The CHA/V (Cheap, Hacky, A/V...) hacks a video signal generator commonly available on Ebay for about 5 bucks. He documents the injection points where you can force in external signals from simple oscillators, and drive the thing wacky. His instructions are great; my modest contribution is how to use one of my 40106 Osc. boards to build those oscillators.
(more detail coming soon)