I just spent about a half hour playing this beautifully designed (and addictive) flash game, Auditorium.
The game is all about directing a stream of particles using small spheres that redirect them in different ways. You want to get the particles running through audio containers that play different parts of the beautiful soundtrack in the game. I guess this game is just a demo so far (only 3 levels). The developer promises up to 20 levels when this thing is done. Take a play, it will be tough to stop.