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.
Wake-on-Shake Hookup Guide
A basic hookup guide for getting started with the SparkFun Wake-on-Shake. The board gives you the ability to put your project into hibernation until bumped or shaken awake using the ADXL362 accelerometer. This means you can design projects meant to stay inert for long periods of time, possibly even several years, depending on the battery type used to power the project.
Sunny Buddy Solar Charger V13 Hookup Guide
How to hookup the Sunny Buddy: a solar-powered, MPPT (peak-power tracking), LiPo battery charger.
12V/5V Power Supply Hookup Guide
In this tutorial, we will replace the 12V/5V (2A) power supply's molex connector with two male barrel jacks adapters.
Getting Started with the MyoWare® 2.0 Muscle Sensor Ecosystem
The MyoWare® 2.0 Muscle Sensor, an Arduino-compatible, all-in-one electromyography (EMG) sensor from Advancer Technologies. In this tutorial, we will go over the features and related shields to connect the sensor to a muscle group.