Polyphasic sleep is one way to get more time. The basic idea is that by splitting sleep up from one 8 hour chuck at night to one or more naps throughout the day can reduce your overall need for sleep. I first discovered the Uberman schedule, which requires you to take on extreme sleep deprivation in order to compress your normally 90 minute sleep cycle into 20 minutes, and then only take 6 20 minute naps throughout the day.
This is the extreme case, and I'm still not convinced that can be healthy, but the less extreme options seem to have some long-term merit. My friend has successfully adapted to sleeping 3 hours at night and taking 3 20 minutes naps during the day, and he says he loves all of the extra time during the night. And apparently biphasic sleep is the norm in some countries. http://www.polyphasicsociety.com/ has some interesting articles about different schedules.
This is the extreme case, and I'm still not convinced that can be healthy, but the less extreme options seem to have some long-term merit. My friend has successfully adapted to sleeping 3 hours at night and taking 3 20 minutes naps during the day, and he says he loves all of the extra time during the night. And apparently biphasic sleep is the norm in some countries. http://www.polyphasicsociety.com/ has some interesting articles about different schedules.