My DS6 is another science lover (ditto I), he did Camp Invention this summer, it was age bracketed and I don't think he enjoyed it as much as he might've. One part of that was to bring an old bit of electronics from home for disassembly which he did enjoy. Contemplating some yard saling for some new things to dissect.

Local hackerspaces will sometimes have open houses (many amusing and cool tools/projects in those.) Another resource can be local manufacturers who can be surprisingly generous in giving individual tours.

And maybe someone already mentioned this site: http://howstuffworks.com
or this book: http://www.amazon.com/The-New-Way-Things-Work/dp/0395938473