I absolutely love visualizations while listening to music, its unfortunate that Ubuntu does not currently have many presets, Fortunately here is a quick way to enjoy a few other visualizations in Ubuntu, personally I think these visualizations should have been installed by default with Rythmbox!
If your in Firefox and have apt-url installed click here to install this with one click!
sudo apt-get install libvisual-0.4-plugins
Ok now Reload Rythmbox and click on Visualization, and you will get a drop down List of the GOOM Alternative Visuals
Hopefully when I get a chance I will port over winamp visuals to rythmbox but, that may take some time hehe