My junior school did a charity day for WaterAid. We had an assembly in the morning where we watched a presentation on the problems people in developing countries (now including Scotland it seems!) have accessing clean water, did water-related lessons: making filters for muddy water out of sand, pebbles, filter paper etc., and finished the day with a huge obstacle course in the playground. The whole school had to go round it holding a cup of water, which was measured out at the beginning and measured again at the end. The 'winner' was the pupil who had the most water left at the end of the obstacle course. It was absolutely brilliant.
Did your school or have your DC's schools done any charity fund/awareness raisers that were a bit original?