This is so cheap and easy, it's nearly cheesy.
This will show you how to reliably photograph lightning for under 3 dollars.
Step 1: Professional Lightning Photography
Lightning photography is some of the most impressive natural/landscape photography there is. Most photographers use high-end cameras with adjustable f-stops, special films, a nice tripod, and a cable shutter release. These are all well and good but even the film is out of my price range.
So first, buy yourself a disposable camera. I used a 1000 speed "high action" camera (because it was the cheapest at ~$2.30) and the results seem to hint that a slower speed would work better (those that developed were flooded with light) and I'll tell you how it goes.
RESULTS: the picture in the Intro was taken with a 400 speed camera. Worked great, especially since the photo was taken at dusk.
A word of warning: After experimenting with Kodak disposables, I've found they don't work the same way. They use a spring trigger, which doesn't fit the following steps. I'd stick with fujifilm (plus, they are generally cheaper)