Music and Audio

Ampache
Open Source, web-based audio file manager which allows users to view, edit, and play their audio files (MySQL and PHP).
http://www.ampache.org/

Audacity
A free, open source software for recording and editing sounds in Linux, Mac OS X, and other operating systems.
http://audacity.sourceforge.net/

MP3 Book Helper
Provides Mp3 and Ogg Vorbis tags editing and file renaming functions. (Delphi) [Windows]
http://mp3bookhelper.sourceforge.net/

MPEG4IP: open source MPEG4 package
MPEG-4 AAC audio encoder, MP3 encoder, MPEG-4 video encoders, MP4 file creator and hinter, IETF standards-based streaming server, MPEG-4 player. Mostly Linux-based.
http://mpeg4ip.sourceforge.net/

Open Sound World
Open-source programming environment that allows musicians sound processing in response to real-time control.
http://osw.sourceforge.net

orDrumbox
Real-time drum machine and audio sequencer written in Java. Online demo, full download, and user manual.
http://www.ordrumbox.com/

SND
Snd is a sound editor that can accommodate any number of sounds and can be customized and extended using either Guile, Ruby, or Forth.
http://ccrma.stanford.edu/software/snd/snd/snd.html

Ubuntu-Studio Project
A site for musicians wishing to use Ubuntu-Linux as their Digital Audio Workstation.
http://ubuntustudio.org/

Zinf
An open source audio player for Linux and Win32, supports MP3, Ogg/Vorbis, WAV and Audio CD playback, SHOUTcast/Icecast HTTP streaming, RTP streaming, with a powerful music browser, theme support and a download manager.
http://www.zinf.org/