All it took was the Arduino, a few wires, six potentiometers, and a variety of knobs -- all available at Fry's. Original site has wiring diagrams, etc.
Some improvements/features I'd like to point out:
- Built into a disposable tupperware container -- this worked really well and could probably be used for many projects since it is dirt cheap.
- Battery-powered with one 9V wired through the switch built into the center potentiometer
- Volume control via a sixth pot in line with the audio output
- Bending the leads on the pots ended up making for some bad connections and hair-pulling troubleshooting -- use caution
- Some practice will let you make some very interesting sounds -- the video was by chance my greatest performance. I have since completely forgotten how to do most of those effects.