According to urban myths, it depends on which hemisphere you live on (north or south) as to clockwise or counterclockwise. Give your toilets a flush to check and see which way we should be officially be stirring!
In my travels I have had a chance to play with this several times as it is not unusual for new people who have not visited the southern hemisphere to want to test it out for themselves. Unfortunately no matter how much you try the water spins in the same direction.