Wow, here’s a really cool LED speaker system that syncs to your favorite music with it’s diamond shaped LED lights. (It’s currently sold out but wait a little and they should be in stock again.)
Now, if you want to build one yourself, refer to my music-syncing light orb DIY for a start.
iLit stereo speakers put on a mesmerizing LED light show as it responds to every beat of the music by changing colors. Sparkling lights race up and down the towers depending on the intensity of the sound. Just plug in an iPod or any music source with the provided connectors (PC/notebook, CD, MP3, radio, or gaming system). Disconnect your music device and the iLit speaker system will respond to the ambient sounds in the room. Features include mirrored speakers for sleek styling, adjustable sensitivity, and volume control. iLit comes with a connection cord and an adapter to synchronize with music players.