I have trained my wife to get up from bed half a hour before me so she can make coffee for me. Then I just look into her eyes using my copyrighted *doggiepuppystare* and voi'la: Coffee brought to bed!
It´s a big piss take that people took seriously and now believe it.
I´ve never been down south either but I´ve read the wikipedia article posted in this thread and seen the "Brainiac" episode where they tested this myth and found out it was completely random and the direction of waterflow had more to do with the shape of the sink instead of the hemisphere on which the sink is located.
It IS true, fundamentally; water WILL tend to drain counterclockwise in the northern hemisphere, and clockwise in the southern hemisphere, but not necessarily in your toilet. The Coriolus effect does exist, and it does apply to water going down a drain, but in the case of a toilet (or other drains that you are likely to encounter), other circumstances have a much greater effect.
In other words, there IS a (very small) Coriolus effect in the draining behavior of your toilet, and your toilet may drain in a direction that seems to be explained by the Coriolus effect, but isn't - this being instead merely a coincidence; and it is perhaps equally likely that your toilet drains in a direction that is opposite to what would be expected from the Coriolus effect, since the Coriolus effect is of negligible magnitude in this situation. Again, quoting the Wikipedia article:
"When the water is being drawn towards the drain, the radius of its rotation around the drain decreases, so its rate of rotation increases from the low background level to a noticeable spin in order to conserve its angular momentum (the same effect as ice skaters bringing their arms in to cause them to spin faster). As shown by Ascher Shapiro in a 1961 educational video (Vorticity, Part 1), this effect can indeed reveal the influence of the Coriolis force on drain direction, but only under carefully controlled laboratory conditions. In a large, circular, symmetrical container (ideally over 1m in diameter and conical), still water (whose motion is so little that over the course of a day, displacements are small compared to the size of the container) escaping through a very small hole, will drain in a cyclonic fashion: counterclockwise in the Northern hemisphere and clockwise in the Southern hemisphere—the same direction as the Earth rotates with respect to the corresponding pole."
So, you should not expect that all toilets drain counterclockwise in the northern hemisphere; and you should not expect that, if you went south, you would find that all toilets drain in the opposite direction (although it would be slightly more efficient, I suppose, if toilets were constructed to behave in this way).
In short, it has no discernable effect on small bodies of water. And it has no discernable effect on large bodies of water either, as tides and thermal flows are of much greater magnitude.
Well, if the bowl is shaped like a half ball and we assume it's exactly in the middle of the equator... If you're in America, it spins counter-clockwise. If in Africa, clockwise. This is due to airflows caused by winds.