I think that the left side is probably the most common, as it is with me personally.
Also, does anyone know of physiological reasons for this? I mean, it's not like mens' penises tend to be crooked to the left or the right or something, so I'm not sure I understand why there's a left/right bias, you'd think it would be random. Maybe it's purely neurological and has something to do with being right or left handed?
I'd be interested to know of any scientific research on this, as this is clearly of the utmost importance.
EDIT: I can't modify the poll, so I'll just ask in comments, how many of you hang in the same direction of your dominant hand (e.g. you're right handed and hang right)? And how many of you hang to the same side of the hand that you wank with?