I like Tim's idea. Never tried that before, but it seems like it will work well, depending on the type of short it is. It seems as if a relatively high resistance short would not cause the bulb to light (is that your experience, Tim?). Also, as Tim points out, tracking it down by pulling fuses will work if the short is in a fused circuit. There are other circuits that do not go through the fuse panel, but you should be able to pull the fusable links to check those.