Play Melody. The only thing that needed to be connected to the board was a cheap Piezo speaker (one leg to a PWM output, the other leg to ground). Then, depending on the key pressed, it sends a signal to the arduino to play a different sound.
LED Cross fade with Potentiometer. Used a potentiometer to cycle between the colors of a tri-colored LED. It was really cool because one can clearly see the combination of colors when its fading one to the other (like purple). Note: Please ignore my voice in the video.
Max MSP. I'm still trying to interface with Max, I'll post videos as soon as I'm successful.