well, i was told that watermelon or grapes would grow out of my ears if i ate the seeds. one time after dinner my mother was eating grapes and accidentally ate a seed. i joked with her and told her they would grow out of her ears. she was in the kitchen cleaning up and came out with a grape stuck in her ear, but didn't act like anything was strange or unusual just to see if i would notice and what i would do. i was little enough to freak out! LOL!
here are some others:
left hand itches you are getting some money (never heard the one about the right hand)
ears burning and someone is talking about you
pregnancy ones:
carry low and across it's a girl; carry high and round it is like a boy.
lots of heartburn means lots of hair.
i have heard the ones about chemicals and figuring out what the baby is, but never did that one myself.
as for the one about sleeping on the stomach to avoid a flat head, this is true, however very unsafe. in fact, since the "back to sleep" campaign, there has been a greater incidence of plagiocephaly (misshapen head) due to babies sleeping on their backs, but there are ways to prevent this and still keep them sleeping on their backs, which is the safest sleeping position for a baby. you can reposition them, turn their cribs or basinets, put them on their sides using a positioner, etc. however, i just used an Amby bed with my last, which is a baby hammock and this always produces beautiful round heads, good-sleeping, happy babies, with little to no colic or reflux problems when sleeping, and is all around the most wonderfully invented contraption i have ever seen (and endorsed by the SIDS foundation of America and Dr. Sears); just wish i had known about it with my girls (not for their heads, but because they all had bad reflux). my baby boy gets comments all the time about what a perfectly round head he has. but i digress
here are some more:
if you make a face for too long your face will stick in that position.
of course there are the ones about "being the master of your domain" and how it can make you turn to stone, get green hands, make you sterile, etc. - any number of ridiculous things.
oh, and another one i heard when i was little was if i saw a naked man before i got married i would go blind!