There is an article out there on the placenta theory. If the placenta is located on the right side than you have a greater chance of boy and the left side girl. The doctor who is theorizing about it sites polarity for the reason (I think). However, I know it was true for both Courtny and I and could be for some of the other girls too. When I went in at 6 weeks for my first U/S, the tech could see that I implanted on my right side and my doc said that this is usually where the placenta starts to form.
I hope some of the other girls have a better memory than I do and can point out the thread and article!
PS I've not heard about sleeping on one side or the other after ovulation.....maybe someone else has!!