Clive Webster has written a tutorial over onexpertreviews.co.uk which uses online service Pushover to send you an alert on your smartphone when your doorbell is pressed. He’s created the doorbell switch with a nice Adafruit button, hooked it up to the Pi and then played the sound of the doorbell from the Pi. It’s an interesting project. Be aware, though, that Pushover is a paid (albeit cheap) service that only works on iOS and Android. Read the tutorial here.
Linux guru Les Pounder has created this fantastic version of Snakes and Ladders called Pythons and Resistors, hooked up to a Raspberry Pi. You press a button to perform a dice roll and magnets and reed switches embedded in the playing pieces and the board trigger sounds to be played if you hit certain squares – the pythons (snakes) and resistors (ladders). It’s a really nice project for which he has provided a complete build-and-code tutorial.