It's been a great run, but today, the 12th of December 2012, will be the last "triple day" of our lifetimes, or at least until the next 01/01/01 in 2101. In observance of that may I present three triples for your bemusement/bafflement/benignant regard. . .
The ternary diagram, which makes ordinary graphs one better by allowing three things, not two, to be analyzed at once.
The triple point, the combination of pressure and temperature where a substance can be in all three physical phases: liquid, gas and solid.
In another excellent observance of 12/12/12, EARTH Magazine has put up an ingenious quiz featuring 12 scrambled geological words, each 12 letters long, and 12-word clues to help you unscramble them. The prize is a t-shirt. Go for it!