How Stuff Works is a sort of 'Cliff Notes' on how things around us actually work. How Stuff Works reviews a great number of products, technologies and natural processes. They range from engine motors, to batteries, to global positioning systems, to nuclear radiation, to boolean logic and much more. New topics are added every week.
Articles often contain numerous photos and diagrams to assist in the understanding of a topic.
The discussion on smoke detectors, for example, points out the two different technologies in use, and then cracks open an actual detector to point out the various parts of the detector that were just discussed. Although a search form is available, the number of topics currently on How Stuff Works is at such a level that you would probably be better off simply scanning the complete list of topics. They are categorized for your convenience. If you would like to know more about how things work, an excellent reference section cites about a dozen books available at your local bookstore or on-line. The obligatory list of links can also be found.