In a very scientific study conducted by Dr. Me, in a test group of 'a bunch of my friends,' I've found that every person on the planet falls into one of two categories: Those who throw out batteries as soon as they wear out the device they were in, and those who save possibly partly-charged batteries in a messy kitchen drawer.
Both ways are generally wasteful because its safe to say in both cases that the batteries will never be heard from again.
Any batteries that read less than 1.2V, discard for recycling. Any that read between 1.2V and 1.4V are partly charged and great for use in a small clock or other small-power device. Any batteries that read above 1.4V are fully charged and can be used in nearly anything for a decent while.
The really tricky part—listen closely—is keeping them organized like this. Lifehacker's reader suggests using double-stick tape to keep the batteries stuck to a labeled card. Or you could go the lazy route and stick 'em in sandwich baggies inked with permanent marker.
Before you know it, you'll be saving money on batteries and—bonus!—you'll get your junk drawer back. For more important things. Like nightlights, rubberbands and take-out menus.