I generally don't take any sort of planned nap in the day because I usually feel lousy afterwards - but sometimes the body just takes over and I zonk out anyway. When I was in Japan last year I lost count of the places the Japanese take siestas. Every second or third parked car would have the driver's seat tipped right back and the driver snoozing away with a paper over his eyes. It was also common in places like Starbucks to see a business-suited office worker, laptop at the ready, coffee on the side with his head down on the table, apparently fast asleep!