I am interested in things that, from the point of view of a a generation or two hence (the people I sometimes refer to as “my hypothetical grandchildren”), will be completely lost or incomprehensible. One kind of thing is what we might call aspects of “microculture”; small parts of the day-to-day culture that just won’t be in the culture at all in 50 years time (there is a loose analogy here with Mark Penn’s Microtrends idea; see his book, ISBN 978-0446580960).
One example is a vague fear of mains electricity. People of my parents’ and grandparents’ generations were, on the whole, rather wary of mains devices. They would certainly turn things off at the mains, and frequently would unplug all the electrical devices in the house as part of the end-of-day routine. This is incomprehensible to me, but I at least aware of it as “something older people do”. To people a generation or two younger than me, I imagine that this would be something that they wouldn’t ever imagine would happen, and it will seem strange to suggest that people did this for more than a transitory few years as domestic electricity was being introduced.
Interestingly, some of this behaviour is returning, with a different motivation, viz. that of saving electricity for environmental or economic reasons.