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.
How to Power a Project
A tutorial to help figure out the power requirements of your project.
SparkFun 5V/1A LiPo Charger/Booster Hookup Guide
This tutorial shows you how to hook up and use the SparkFun 5V/1A LiPo Charger/Booster circuit.
Buck Regulator Hookup Guide
Get started with SparkFun's newest Buck Regulator Boards - the BabyBuck and the Buck!