Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Magic Music Visuals - Fully-customizable and highly responsive visuals for live and recorded audio & MIDI.
TwistedWave - TwistedWave is one of the unique audio editors that allow you to edit your music file online without any installation.
MilkDrop - 3D audio visualization plugin, compatible with WinAmp plugin API
Radium - Radium is a music editor with a new type of interface.
Kauna - Kauna is a music visualizer. Kauna renders any sound reproduction in system.