javashout is a program for shouting mp3s to a shoutcast server. It runs on any system, takes very little cpu time and has some nifty features. You can remotely connect to it via telnet and change options while it's running. You can also attach another shout to the back of javashout, allowing you to alternate between using a playlist and manually choosing songs painlessly without skips or jerks in the sound.
jMusic provides a library of classes for generating and manipulating music, and is a solid framework for computer assisted composition in Java. jMusic supports composers by providing a music data structure based upon note/sound events, and methods for working with that musical data. jMusic can read and write MIDI files, audio files, and its own .jm files. jMusic is designed to be extendible, encouraging you to build upon the functionality of jMusic by programming in Java to create your own music composition tools.
juked is a daemon that turns a server into a music jukebox. Clients communicate with the server via TCP/IP using an XML protocol. It features playlist support, user authentication (optionally with PAM), and random track selection. Audio decoding is done using XMMS plugins, so both Ogg and MP3 are supported. Track (song) information can be stored internally or in a MySQL database.
KegTracker is a GTK+-based MOD editor for Linux distributed under the terms of the GPL. It uses a modified version of the xmp library by Claudio Matsuoka and Hipolito Carraro Jr. KegTracker and can play all music modules supported by xmp, which is just about everything except Impulse Tracker modules. Its graphical interface includes Track Display, Order Display, Instrument and Sample Display, as well as basic controls you'd expect in a tracker. It also features a cool starfield about box by Rasterman.