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.
LilyPad Simple Power Hookup Guide
A basic guide for getting started using the LilyPad Simple Power with LiPo batteries.
Measuring Internal Resistance of Batteries
Classroom STEM activity that has students build a battery from a lemon, measure the open and closed circuit voltages, and determine the battery's internal resistance.
SparkFun RTK Express Hookup Guide
Learn how to use the enclosed RTK Express product to achieve millimeter level geospatial coordinates.