Most evenings I'm either watching TV or a movie, working/playing on the computer or chatting with friends; none of these activities require a huge amount of room light. Generally I put a light on low just to provide enough illumination to avoid tripping over the cat when I go to the bathroom. I have a pocket LED flashlight with a single 3W Cree LED in it, and it seemed to me that it put out plenty of light for low-level illumination of my living room for those sort of activities. So I created an LED room light with a rechargeable battery in it, and installed solar cells to recharge the battery. I prop the unit outside in the sun when I go to work in the morning, and in the evening it's charged up and ready to light up my living room.
Update: I've been poking around and I see that I'm far from the first person to have this idea -- there are a lot of very nice "sun jar" designs which I was unaware of. I think my room light is different primarily by having a larger battery and solar collecting area, which allow it to drive the LEDs much harder and put out a lot more light. My unit is very esthetically challenged compared to most of the sun jars, but it's much brighter.