I was in Safeway a couple days ago and saw these in the discount Halloween section. They are the flickering LEDs that look like a candle, usually put inside a jack-o-lantern when someone doesn't want to use a real candle. Normally, I would never pick up something like this because they use really big button style batteries, not the variety that would normally be lying around the house. However, each pack contained two LED candles and spare batteries for both of them for $2.50.
According to the packaging, each battery will last about 48 hours. So, two lights and two spare batteries in one package should last around 192 hours. Now, these aren't particularly bright and they flicker (they aren't as bright as a regular candle), you probably couldn't read by these, which is probably why they last so long. But for a small, disposable, subdued light source that's not a bad deal.
I picked up two packages for five bucks, and put them in my Home Hurricane/Emergency Kit. I have plenty of other light sources, including a lantern and the real candles that these are supposed to simulate, but five dollars for 384 hours of light is pretty cheap.
Plus, these interest the geek in me. Looking at these I already am seeing how I might be able to modify them to make them more effective. First would be just cutting off the plastic 'flame' to see how much more light I'd get. second would probably be trying to bypass the 'flicker' circuit so it will provide a steady glow. Those changes might, however, adversely affect the battery life. Or you could probably cover the 'flame' in red permanent market, make some convenient "night" lights, scatter those around a house or camp.
That's what's nice about discount electronics, you don't feel bad messing around with them.
If I make any of those changes, I'll be sure to post an update.