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.
How to Power a Project
A tutorial to help figure out the power requirements of your project.
Battery Babysitter Hookup Guide
An introduction and getting started guide for the Battery Babysitter - a flexible LiPo battery charger and monitor.
Current Sensor Breakout (ACS723) Hookup Guide
Learn how to measure the current consumption of your project using the ACS723 Current Sensor.
ATX Power Connector (4-Pin) Breakout Hookup Guide
Do you need to power a project with 12V and 5V from one wall adapter? The ATX power connector breaks out the standard 4-pin computer peripheral port for your 12V and 5V devices!