The following video really caught my attention on Create Digital Music. Created by Peter Kirn, an array of motors, wires, and cardboard were used to simulate the sound of rain. The arrangement of the cardboard, the type of wire, and the speed of the motor distinguished all different types of rain:
http://createdigitalmusic.com/2011/05/exquisite-sonic-sculptures-made-with-motors-and-cardboard/
In another post by Peter Kirn, he is able to create a melody simply from the sounds of an alarm clock:
http://createdigitalmusic.com/2011/05/music-for-dieter-rams-alarm-clock-becomes-melodic-minimal-treat-music-and-good-design/
I also found this to be very interesting; a record made completely from paper and rotated manually by one's hand:
http://createdigitalmusic.com/2011/04/a-record-player-made-from-paper-as-the-flexidisc-lives-thanks-be-to-pythagoras/
The following two videos were some other ideas that caught my attention: a dance floor that played different loops in different squares and an example of a theremin made from a kinect (a popular video game)
http://createdigitalmusic.com/2011/04/a-kinect-based-instrument-polyphonic-theremin-no-april-fools-joke/
http://createdigitalmusic.com/2011/04/bugs-on-the-game-grid-synplode-makes-step-sequencing-tangible-for-an-interactive-dance-floor/