The thing is, I think my interests are perfectly normal...until I'm telling someone about them and their face/words let me know that my interests are not at all typical.
Radio Shows- why that's not still a thing, I have no idea
Wax cylinder recordings
Cooking with rations during WWII
Old instructional videos- on manners, relationships, grooming, etc. It pretty much doesn't matter.
Old recipes for forgotten food that everybody used to cook and nobody's heard of anymore
Home items everyone used to have but doesn't anymore (ex: breadboxes)
Home items that used to make life easier/more comfortable but have somehow been forgotten or are no longer used (dumbwaiters, home relaxation kits, laundry chutes, cooling cabinets, milk doors [I'd love one of those for home deliveries])
3D printing (whether it's for merging art with cell phone covers, or printing a copy of a skeleton for study, or 3D printing a house, etc.)
Home automation devices (I look forward to a fully automated retirement someday)
Old coded communication techniques (flower language, signal flags, phonetic radio alphabet [had that memorized when I was a kid], distress signals, etc.)
Old school tests, textbooks, and assignments from the nineteenth century through the 1960s or so- entrance exams and final exams in particular
Solar ovens
Sustainable architecture- green materials, passive and active green features, etc.
Community gardens/urban gardens
Kit houses from the 1900s
Past visions of the future (Disney's Tommorowland and such)
Animal tracking and old traps
Natural dye sources, and the colors they produce
Time capsules, especially accidental ones
Old fallout shelters, especially the ones designed/built by the homeowner
Old airline, cruise, and train menus
How influenza impacted daily life during WWI- precautions people took, schools and churches and such being used to quarantine/treat
Automat restaurants
I'll post more if I think of more