Audacity is a cross-platform multitrack audio editor. It allows you to record sounds directly or to import Ogg, WAV, AIFF, AU, IRCAM, or MP3 files. It features a few simple effects, all of the editing features you should need, and unlimited undo. The audio I/O uses PortAudio, which fully supports OSS, Mac OS X CoreAudio, and Windows WMME, and can be compiled with support for ALSA and Jack.
A fast multi-track audio editor and recorder for Linux, BSD, Mac OS, and Windows. Supports WAV, AIFF, Ogg, and MP3 formats. Features include envelope editing, mixing, built-in effects and plug-ins, all with unlimited undo.