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.
Benchtop Power Board Kit Hookup Guide
Need more power? This Benchtop ATX Power Supply Kit should help give you the boost you need to power those energy hungry projects.
Hookup Guide for the SparkFun RedBoard Artemis
Get started with the RedBoard Artemis - all the functionality of the SparkFun Artemis module wrapped in the familiar Uno R3 footprint
smôl Power Board AAA Hookup Guide
Small in size, small on current draw. It's a smôl world! This guide will get you up and running with the smôl Power Board AAA.
Breadboard Power Supply Kit 5V/3.3V Quickstart Guide
Quick start guide for the Breadboard Power Supply Kit 5V/3.3V