Cocoa mulch looks a lot like coffee grounds in a picture, so you'll just have to see that post for an idea of what I'm talking about. But it's lots of fun and the smell may make you run for your nearest store in search of chocolate.
From what I've seen, cocoa mulch comes in two varieties. The small kind is the kind that looks a little like a cross between flake cereal and coffee grounds from a distance. It tends to get dusty when it's completely dry but the smell lasts a long time and you can keep it for at least once school year if you put it away dry. You can use similar tools and toys as you can with sand.
The other kind of mulch is really more like bark. It has larger chunks that are too big to scoop. The kids enjoy using it for construction play as well as hiding toys. We did have a problem keeping it from getting smelly in a bad way after awhile. Someone thought this was because it still contained some plant oils in it that went rancid, but we really don't know. In any case, this is the kind of thing you buy on sale since you know it won't last forever.