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.
The Java Media Framework (JMF) is an API for incorporating audio, video, and other time-based media into Java applications and applets. It is an optional package that extends the multimedia capabilities on the Java2 platform. The Blackdown JMF is a Performace Pack which includes native code in order to provide faster processing and tighter integration with Linux than the all-Java version.
The FAAC project includes the AAC encoder FAAC and decoder FAAD2. It supports several MPEG-4 object types (LC, Main, LTP, HE AAC, PS) and file formats (ADTS AAC, raw AAC, MP4), multichannel and gapless en/decoding as well as MP4 metadata tags. The codecs are compatible with standard-compliant audio applications using one or more of these profiles.
MP3do is an "all in one" bash script. It is useful for decoding and mastering audio files. It can decode a list of MP3 or Ogg Vorbis files to WAV or CD-R, auto-convert poor quality MP3s to 44100Hz stereo, check whether all files fit on a CD, normalize all WAV files (adjust the volume to a standard volume level), and burn a CD.
StreamBOX-LiveCD is a KNOPPIX-based boot CD which is specially designed to stream MP3s. It also includes some programs to stream in the Ogg Vorbis format, to cut audio, to view video and video streams, and to perform other similar tasks. It is intended to be used at smaller radio stations.
Transcribe! is an assistant for working out a piece of music from a recording. It offers many features aimed at making the transcription job smoother and easier, including the ability to slow down the music without changing its pitch, and to analyse chords and show you what notes are present.