One of the nice things about using PulseAudio as a sound system is that you can easily plug visualisations into the chain - projectM has versions for input from both PulseAudio and JACK. There's a HOWTO on the Ubuntu forums - use the latest released version rather than getting projectM through subversion.

It's a slightly odd compilation: you have to create a folder, extract the libprojectM, libprojectM-qt and projectM-pulseaudio source archives into that folder, then compile them each in turn: cmake .; make; sudo make install (checkinstall doesn't seem to install all the presets, for some reason).

Once it's installed, run projectM-pulseaudio and the visualisation should start up in a new window. Press 'm' to get to the menu: there are lots of options to tweak to get good, fullscreen performance.