Something I just noticed recently is the fact that crossword puzzles are rotationally symmetric, i.e. if you rotate them 180 degrees, the black and white spaces are in the same locations. 
[Image: crossword.png]
This doesn't really help anyone solve the puzzle, and it doesn't serve any other practical purpose besides making the puzzle look visually pleasing from a distance. 

On a somewhat related note, NY Times crossword puzzle expert Will Shortz wrote an article on how to solve them (via Kottke), saying, "If you get stuck on a puzzle, a time-honored technique is to put it aside and return later."  Amen to that. #entertainment