If you're like us, we're getting ready for that big ol' hurricane Irene (we're in Manhattan now, Long Island tomorrow--yikes). Since we're pretty positive we're going to lose electricity for some amount of time, even up to days, getting all the power out of our Windows Phone is key.
One easy method "Mango" users can enable now is the Battery Saver feature by going to Settings --> Battery Saver --> "Turn on Battery Saver now, until my next charge". The phone will of course still work, but background services and push email will be disabled--which is a great way to squeeze out a few more hours from your phone while you pray for the lights to come back on.
It also wouldn't hurt to bump your backlight to "Low" under Settings as well. Good luck everyone.