In relation to "White Rabbit" mentioned above, I was camping w/ some friends in college, and as we were sitting around the fire one kept repeating "I hate white rabbits" under his breath (really!)
When I asked him why, he said that he learned in the Boy Scouts that if constantly said "I hate white rabbits" the smoke from the fire would not blow on you. (Must be a Minn. thing)
And to the Macbeth tradition/superstition, I took a class in collect were all we did each week was see various plays in Chicago and discuss them (great class/tix were part of class fee/all the actors were wonderfully kind).
We had just finished watching the company perform Macbeth, and while they were preparing for the evening show, they invited the class back to talk. Needless to say, you had about 20 people talking and saying Macbeth over and over for about 10 min., when the director came back, heard what was going on, and chased everone out (including the actors) from backstage yelling at us that we had jinxed the show... and he was from eastern europe, so I guess it is pretty wide spread.