Just something I've been thinking about while reading neuroanatomy...and I knocked my table clock over...
Time flies when you're having a good time. Conversely, it seems to slow down in times of boredom or extremely intense situations (like when you drop something, and you go "Nnnnooooooooo!!!" in slow-motion :)).
Einstein proposed that time and space are relative. What if it applied to humans' concept of time itself? There could be a subsystem in the nervous system (probably in the brain) that mediates the person's "sense" of time...during times of non-danger, or more specifically, enjoyment or fun (in medical terms, those described as inducing "parasympathetic" responses), the system is inactive and time seems to move faster. But during stressful situations ("sympathetic") it is activated and the person has a more perceptive sense of the flow of time. It could be an involuntary body-function (physiologic) mechanism...though it doesn't really explain boredom...
Or, another idea, it could just be the person's awareness. If he/she is absorbed in something, the person focuses on that instead of other things...while in times when there is nothing to focus on, as in the case of boredom, more attention is devoted to "time" in general. But then again, this wouldn't really explain the "falling object phenomenon".
Haha...just some food for thought...any other bright ideas about the subject?