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.
ESP8266 Powered Propane Poofer
Learn how Nick Poole built a WiFi controlled fire-cannon using the ESP8266 Thing Dev Board!
How to Build a Remote Kill Switch
Learn how to build a wireless controller to kill power when things go... sentient.
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!