Gizmodo has a page of "9 Extraordinary Collections of Totally Ordinary Objects", including "A History of the World in 100 Objects" and a Smithsonian exhibit called "Souvenir Nation: Relics, Keepsakes, and Curios." I enjoy viewing collections both in person and online. People collect all kinds of fascinating things, and I've known folks who collected shells, buttons, Barbie dolls, teapots, marbles, keys, books, fountain pens, bird sightings, stamps, quilts, Star Wars memorabilia, owls, coins, autographs, bells.... The objects one can collect are as numerous as people who collect them. There seems no end to it.
I don't collect anything, although I still have the rock collection I began as a project for a Girl Scout badge. I do have a few conglomerations of like objects I just somehow ended up with along the way. For example I have a shelf with bells:
I have a few elephants:
I'm gradually getting rid of many items that don't bring me joy, as recommended by Marie Kondo, but the elephants and the bells remain. I don't add more, and I don't consider them a collection, but that's as close as I get.
Having a formal collection, researched as some are, isn't something I have any interest in, but I like looking at what other people are interested in. Just look at these beautiful marbles, the largest private collection of movie cameras, a collection of 1,400 automobiles, this woman's teapot collection, these collections of Pez dispensers, a button museum, an online video collection of obsolete objects, Paul Johnson's collection of 3,479 pencil sharpeners (no duplicates), and this collection of historical maps. Fascinating!