G-force and whitecap are the best I've come across and i think that the itunes visualizer is a cut down version of G-force. G-force runs v.fast in OS9 but somewhat slower in X.
You can find both at
<a href="http://www.55ware.com/" target="_blank">http://www.55ware.com/</a>
There are others out there as well, so happy hunting.