Audacity

Audacity is a free sound editor. You can use it for recording audio or editing existing audio. It supports the many different formats and is useful for converting one format to another. It runs on most operating systems. It also has the ability to add effects like noise reduction, slowing playback speed, and more. For a full list of features see http://www.audacityteam.org/about/features/.

Uses in classroom teaching: Uses in studio teaching:
 * Record lectures for podcasts
 * Record aural skills assignments
 * Recording student lessons
 * Saving files in different formats for audition submissions

http://audacityteam.org