Meet Philip's SpotOn LED lamp. I just bought two and I love them. Basically they only consist of batteries, LEDs and a motion sensor. Because LEDs have really low power consumption you can stick these babies anywhere around the house where you need a little extra light: cupboards, hallways, kitchen cabinets. No hassle with installation, power supply, etcetera. Just double sided tape will do it. Brilliantly simple, and only possible since the recent advent of cheap, powerful LEDs. The only thing I think it lacks is a light sensor, because right now any motion triggers the lamp to switch on, even when there's plenty of daylight. And maybe the light could be a little brighter. But otherwise: lovely.

See also this pretty enthusiastic review on Apartment Therapy.