Magnetosphere for Mac

From Barbarian Group Software:

Here is this thing that does stuff in iTunes. There is magnetism, there is gravity, but on top of all of that, there is awesomeness. Watch as all the dots and ribbons go bouncy bouncy when you play music and trigger this visualizer. This is the future of visuals.

By the way, don't go crazy with the A and S keys - they add or subtract a hundred particles at a time - tap once or twice and wait for the results. If it starts acting poorly because you hit a bunch of keys, just quit and restart.