Whew! have you tried Sudoku yet? My wife and I have been having contests. We both go to www.websudoku.com and on separate computers try to solve the same puzzle. Here is an example. 
The idea is simple. Fill in the blanks such that no number is repeated in a row, column or 3x3 square. There are over 8 billion games at this site!
The cool thing is that the young man who programmed this site is into math and he plots the times people take to solve the puzzles. You have to be pretty sharp to beat the average! My son and I worked together on the "evil" level and it took us 64 minutes to solve!
There *is* more to life than craps. :-)
