How I loved to play with my mothers clothespins myself! She has a huge amount in all kinds of colours and shapes, from plastic and wood. Even today- when I am at my parents house and help her to hang the laundry- I choose always the matching colour to the item I want to hang :o)
My daughters love to play with my clothespins too- allthough I don't have so many (our laundry is mainly washed, dried and folded in the local "laundry-store").
So many things you can do with them- sort them by colour, put them in tins and boxes and take them out again, hang them on the line, make rows with them, put them in a jar and shake....