In an old Scientific American "The Amateur Scientist" column, there was a device for finding the direction of lightning. I really love lightning, and I would have loved to build it, but the plans used CRTs and tubes, so it was nearly impossible.
What did make sense, however, was that the signal received was an audio-frequency electromagnetic signal.
My idea is to build a loop DF antenna and connect it to a phono preamplifier, and feed the signal to the stereo sound input of a PC. From this information the strength and direction of a lightning strike should be determinable.