If you're interested in making musical toys for younger children, interactive devices or just making some noise this project by Kevin Hietala will be of interest. He has created a layered structure from laser-cut pieces that stack together to form a person's bust, and fitted inside this an Arduino with a simple speaker. It's programmed to play a tune when the head of the sculpture is removed, which may seem simple but would amuse younger children and is also an interesting lesson in itself. A quick demonstration of this is in the following video:
If you're interested in working with making sounds and tunes for various reasons we have a neat little SOUND: sound and buzzer module:
It can be used as a noise-maker driven by your microcontroller for audible feedback of events, and it can also be used as a knock-detector input to sense events and react to them. Includes a built-in 1M resistor to allow the piezo element to detect shocks. For more information and to order, please visit the product page here.