Napping: the expert's guide | Life and style | The Guardian
http://www.guardian.co.uk/lifeandstyle/2009/jan/27/napping-guide-health-wellbeing

For years, napping has been derided as a sign of laziness. We are "caught" napping or "found asleep at the switch". But lately it has garnered new respect, thanks to scientific evidence that midday dozing benefits both mental acuity and overall health. A slew of recent studies have shown that naps boost alertness, creativity, mood, and productivity in the later hours of the day.

Daniel Tenner has spent a lot of time thinking about (and taking) naps. What follows is his experience learning to master 20 minute power naps even though he normally takes 30 minutes to fall asleep.