2 Chime Doorbell

Doorbells can be simple or complex. This is the smallest surface area I could create and still have two chimes both sound with the one button press. Youtube tutorial shows how to hide the doorbell inside a wall as well.

You can also connect this to a T Flip Flop and then to a door control and have the door open after the doorbell has sounded.

Youtube Tutorial

Minecraft 1.5.1