@ catholiver: People do collect sewing buttons. It is, as are most arcane hobbies, a highly structured process in which buttons of certain types are wired onto 9"x12" cards, and when entered into competition are judged according to criteria known only to the initiates. Tania’s faves are bats, cats and Moonglows, those last being a kind of glass button pioneered by the Czech factories after WW2 in which a clear glass layer is laid over a translucent colored base. I am amazed to have remembered that. Anyway, they get together at some inexpensive locale to compete and buy and sell. Tania and a fellow collector from Nashville do a Buddies Week there most years.
The advantage to collecting buttons, rather than cars and cookbooks, is the amount of space each thing requires. I am obviously at a major disadvantage here.