The Vision Sciences Society just announced the winners of this year's 5th Annual Best Visual Illusion. First prize was the project entitled "The break of the curveball". Click on the link and explictly follow the directions on the right side of the screen. I don't want to say anything more about this neat illusion!
Why can't you hit a curve ball? Why can't major leaguers hit a curve ball? This visual illusion helps us understand the pitch a bit more.
PS - I could never hit a curve ball in high school.