I discovered this gem of an app a couple months ago thanks to an article on Lifehacker. Lifehacker's app recommendations can be hit or miss, so I took this with a grain of salt. But after trying it for a couple months, I couldn't be happier with the results and it's become one of my absolute favorite apps. I've noticed a few of you mentioning it in various forums as well, so apparently word has gotten around! But to those of you who have yet to try Greenify, I would highly recommend it. Basically it "auto-hibernates apps". So, for instance, if you have the Facebook app, but don't necessarily care to have it running in the background eating valuable battery life, Greenify will hibernate that app for you. It's very simple to set up and it has definitely extended my battery life after adding around 7-8 apps to my hibernate list. I'm attaching the Lifehacker article and Google Play links below.
Lifehacker: http://lifehacker.com/greenify-auto-hibernates-apps-youre-not-using-to-save-513922193
Play Store: https://play.google.com/store/apps/details?id=com.oasisfeng.greenify
Lifehacker: http://lifehacker.com/greenify-auto-hibernates-apps-youre-not-using-to-save-513922193
Play Store: https://play.google.com/store/apps/details?id=com.oasisfeng.greenify