One of my favorite math resources are the ones found while walking (think: sticks, pinecones, rocks) or while staring into the kitchen pantry (think: macaroni, beans, straws). Shells are the most fun for me to collect. I love to scour the coastline for sea treasures when we visit the Oregon Coast. I have collected quite a few over the course of the years and I love to bring them out during math practice.
I like to call one of the fun games we play, "Shell Lotto".