Okay, I admit that this is a little off-the-wall, but at the same time it's very cool. If you've been around audio for awhile you've heard of piezoelectric mics and tweeters. They're cheap and not abundantly useful, but they are interesting in that they're built around crystals that have the unique characteristic of developing an electrical signal when the crystals are physically compressed, even by something as small as sound pressure.
Here's an interesting video about how you can make your own piezoelectric crystals in your kitchen, and turn them into a microphone. Below the video is a recording using the kitchen-made mic. Thanks Marsha Vdovin for turning me on to this post.
First recording using Rochelle Salt piezo crystal made from baking soda and cream of tartar by leafcutterjohn