Wikipedia
VSXu
VSXu'' (VSX Ultra'') is an OpenGL-based (hardware-accelerated), modular programming environment with its main purpose to visualize music/audio data and create 3D effects in real-time. Available for Windows and GNU/Linux. It is currently released as free software under terms of the GNU General Public License v2 and maintained by Vovoid Media Technologies AB. VSXu is built on a modular plug-in-based architecture so anyone can extend it and or make visualization presets ("visuals" or "states").