Reducing Arduino Power Consumption
Contributors:
Alex the Giant
Alex the Giant 
Resources and Going Further
More information on low-power modes and options can be found in the datasheet for the 328P.
For more power-related fun, check out the following SparkFun tutorials.
Battery Technologies
The basics behind the batteries used in portable electronic devices: LiPo, NiMH, coin cells, and alkaline.
Hobby Servo Tutorial
Servos are motors that allow you to accurately control the rotation of the output shaft, opening up all kinds of possibilities for robotics and other projects.
Nuclear Battery Assembly Guide
How to put together your BYOT (Bring Your Own Tritium) Nuclear Battery Kit!
Buck-Boost Hookup Guide
This tutorial shows you how to hook up and use the SparkFun Buck-Boost board.