Here's an unamplified Piezo element for breadboarding sound applications (making or detecting sound!)
Piezo elements are actually one of the coolest crystals you'll play with. Flex them, they generate a voltage (pretty high, actually). Pass power through them, and they'll flex. Do it fast enough, and they'll start to make a sound! So besides making annoying little beepy noises, you could use it as a sensor to detect a knock or other similar vibration.