I've been meaning to do something like this for awhile, but Saturday when we were at the grocery store, Ethan and I picked up two bags of dried pinto beans. Just to give you an idea, I paid just under $4 for two large bags. I told him that they were not for eating, but that we were going to do something special with them. Intrigued by the idea, he insisted on holding them for the remainder of the shopping trip, as well as in the car on the way home (Blast, I totally should have gotten a picture!)
That being said, I didn't have a whole lot of time to get things together when we got home (notice how he's still wearing his jacket!) I grabbed a serving spoon, some plastic measuring cups, a large bowl, a shallow tray, and an empty plastic sugar container. He really had a good time scooping and pouring the beans--an activity we duplicated the next day, at his request.
I'd give this activity a solid A.