Audacity

Audacity is an intuitive, user friendly Audio editor and recorder for Mac OS X. With this software you can record with any sources, e.g. a Microphone. These recordings can be saved as MP3-, Ogg-, Vorbis- or Wave- files.

You can also cut, copy, or mix your favorite sounds. Of course it is also possible to change the speed, pitch and more. The numerous existing functions can be extended by plugins as needed.