Apple has added three new visualizers in the version of iTunes that is built into the latest build of leopard. The new visualizers are called Lathe, Jelly, and Stix.

Lathe: A floating fountain of particles that pulsate to bass (very responsive to bass drums)

Jelly: A quick moving kaleidoscope of multicolored bright LED-looking lights

Stix: A streak of light that changes speed and color to the music and reflects on the "floor" of the visual.
Apple is expected to release Leopard in October.