ThinkGeek has a binary clock, showing time in binary format using LEDs. (Kartik really likes them btw!) I was looking around, and found a nice article on how you can build your own binary clock! It sounds like a cool one day hack. Not sure if I will ever do it, but just putting it down here for reference!
Yes, It is in my wishlist too:
http://kartikm.wordpress.com/wishlist/
Damn you! I was about to prepare that kind of project myself, but being lazy, I’ll just use this schematics 😉