Audacity

Product: Audacity v1.3.12 RC 5
Website: http://audacity.sourceforge.net
Type: Open Source
Requirements: Windows XP/Vista/7

Audacity is a free, easy-to-use audio editor and recorder. It supports all common editing operations, plus it will mix tracks and let you apply plug-in effects to any part of a sound. It also has a built-in amplitude envelope editor, a customisable spectrogram mode and a frequency analysis window for audio analysis applications.