I took a shower this morning and came downstairs and there was water on the dining room table. The floor in the bathroom is completely dry and the ceiling above the dining room table is completely dry. However, it looks like there is a weak spot in the ceiling (and possible tiny crack) above the spot on the table where the water was. I'm not sure what to make of these. Please let me know what you think the problem could be and what action I should take.

Put newspaper on the table and turn the shower on for a minute. If the drips line up straight below the crack you found your area. Open the ceiling, its wet above and must be replaced. The open ceiling will help you see the leak. It could be the drain, mixing valve or shower pipe above the valve.