The 12 Cent Calendar
Looking for a cheap calendar that will never run out of pages? Think you're clever enough to think like a computer? Then this is for you. All you need are 12 pennies, a piece of cardboard, and an X-Acto knife.
Here's the finished calendar. It uses heads or tails to spell out a binary number for the day of week, month, and date (the binary system is used internally by all modern computers). In this configuration, Wednesday, December 31, 2008, is represented. If this explanation is gibberish to you, pop over to evil mad scientist laboratories for a breakdown and some tutorials on binary numbers.
Images via evil mad scientist laboratories.