Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Jokosher - Jokosher is a simple and powerful multi-track studio.
TwistedWave - TwistedWave is one of the unique audio editors that allow you to edit your music file online without any installation.
DSP-Quattro - DSP-Quattro
Radium - Radium is a music editor with a new type of interface.
SoundEngine - Freeware audio editor/recorder