I have a very small rainwater leak that allows a cup of water or so after each rainstorm. It accumulates in the low spot under the aft berth near the raw water intake. Based on the contour of the hull, it could be coming from anywhere on the starboard side as far forward as the galley. This picture shows the location where it accumulates, although I removed the water before taking the picture:

I was on the boat just after a rainstorm last week and saw the water present, but was not able to trace the trickle of water to its source. I'll be unable to work on it again until I'm on the boat while it is raining, and that happens relatively infrequently. (I suppose I could douse it with water from a hose, though.)
FYI, the area stays bone dry unless it rains, so that seems to eliminate the domestic water system as a source of the leak.
Do any of you have experience with this, and can you suggest possible deck penetrations that are more likely than others to be the source?