Try radically changing your food intake (patterns and/or content). E.g., http://wholehealthsource.blogspot.com/2010/12/interview-with... or http://en.wikipedia.org/wiki/Intermittent_fasting ; When varying mine, I switch from periods of being a night owl to almost being a morning person, and from needing 8 hours to 6 hours (and also at different times - e.g. sometimes it's 2-9 am, sometimes it's 11pm to 6am)

Experimenting with yourself is cheap, interesting and rewarding. Not always easy, but definitely worth trying.

Also, read Seth Roberts at http://sethroberts.net/self-experiment/ - he (and his reader) report about a lot of experiments regarding sleep and mood; among those I remember: - eating lots of animal fat (bacon and/or butter) improves sleep. Standing on one leg for extended periods of time improves sleep (probably the easiest way to fatigue yourself into sleeping).