Power napping is an effective, well-documented method to increase wakefulness during the day. If you have to get by on very little sleep, learning to power nap can be an invaluable tool to stay awake and remain alert during the day.
Extreme power napping (also known as polyphasic sleep or Uberman's Sleep Schedule) involves getting most or all of your sleep from power naps without the need for chemicals such as caffeine. Many successful extreme nappers thrive on a total of two hours of sleep per day, often experiencing greater alertness and concentration than monophasic sleepers. Check out this youtube video for more information:
Also of interest is this documentary by sleep researcher Claudio Stampi: