This has been a favorite activity around here lately. A simple underbed box lid, lots of rice, and any “tool” that suits H.’s daily fancy. He raids his kitchen(or mine) and car drawer to collect a few good things for pushing, scooping, pouring, and dumping. The rice feels great in your hands and has a nice sound as its being scooped and poured. We have about 2 pounds of rice here, which has proved to be plenty. It was dyed for a craft project and then never used. Really, I would advise against it for this kind of activity—the dye does come off on little hands and who knows what else.
The lip of the lid is just enough to keep (most of) the rice from spilling out on the floor and low enough so little arms can reach everything. When it gets warmer, we will move this outside on the porch and then 18 month old T. can get in on the action. For now its a good “while baby brother naps” activity. When we are done, I just tilt the lid up and dump the rice back into a large container for next time.