Update: Pixxy now works in CS6!
Fractallonomy Pixxy is a set of plug-ins for After Effects that can convert music into visual effects directly with no keyframing (via). It comes with 2D and 3D plug-ins that can use chaos, mathematics, and audio input, and over 100 tutorials and examples. According to the developer, "Some of these have already appeared in some form within DigiEffect's last product, 'Fantazm', just in case you have seen the name Pixxy before. However, the plugs have been heavily modified since then."
Someday iTunes visualizers like Trapcode Klangfarbe and AlphaOmega could also be ported to AE.