My wife came up with the idea of having a lamp in the wardrobe which should operate under the following set of circumstances only: there's sufficiently dark in the room and someone is standing in front of it with the door open for a certain amount of time. More precisely, the typical usage scenario would be the cold, dark winter mornings. It's October and the winter is nearly here - the time has come to build this project.
A word on the versions. The NE555 seems to be the most common DIP 555 on ebay, for instance. It will work in most cases. I doesn't work properly below 0 *C or above 70 *C. The SA, NA or SE are better options in terms of temperature tolerance. The only problem I found was that shops usually don't keep the SA, SE or NA in through hole version, so you'll have to go for the SOIC or even TSSOP and then a converter if you want to use it for through hole prototyping. Just in case you wanted to make a cool outdoor application. It's not a very big deal and the converters are cheap, too, but SMT is a bit of a pain when it comes to hand soldering.
The monostable timer application of this circuit is explained on page 9 of the datasheet. I laid out the circuit slightly differently below.
The time for the one shot pulse is 1.1 Ra C, where Ra is a pot in this case to adjust the timing if needed. I included some typical values for the other capacitor and resistor. The 555 is a brilliant little circuit, it's well worth playing around with it.
Download the schematic here: