I found an interesting link from a page about sleep cycles--
BBC - Science & Nature - Human Body and Mind - Sheep Dash!
The "Sheep Dash Test"
This little applet will time your responses (you have to click a "tranquilizer" button every time you see a sheep dash out into the yard) and determine roughly how sleepy you are.
It's 12:01AM here, I'm totally ready for bed, and I got the "Bobbin' Bobcat" rating.
The original link I was viewing, for anyone who's interested, is this: Sleeping Well: Understanding Sleep Needs, Cycles and Stages