The platform independent and Open Source driven audio editing software Audacity has been released in version 2.0. Audacity is available for Windows, Mac OS X and Linux. Many people say, Audacity is simply one of the best software audio editors with a huge amount of well designed built-in functions (fading, normalizing, vocal remover etc.).
Although the GUI should imho still be enhanced in comparison to its commercial competitors (Steinberg Wavelab, Sony Soundforge, Adobe Audition etc.), Audacity is a must-have, as it is free and from a technical point of view it is impressively powerful.