x10mp3 is a plugin for XMMS to control it using X10's Mp3Remote, which comes with Mp3Anywhere, Mp3Anywhere 2000, or DVDAnywhere. It has all the functionality of X10's BOOM2000 software for Windows, plus other handy features like muting, skipping around inside tracks, and balance control.
mixplayd is a multi-channel MP3 player daemon controlled over a TCP port. It has all functions like play/pause/stop/seeking plus special mixer functions. The number of channels and sound devices (including named pipe support) can be changed at run time. It is meant to be used in conjunction with a playlist-maintaining client.
Mplinuxman is a file manager program for the MPMan F60 USB portable MP3 player. It can send and receive files using an intuitive graphical user interface (GTK2). It features playlists, ID3 tags on the player, hot-plugging support, and a random list function to fill up the available space on the device.
BackPlay a program that plays music files from a folder in the background. At login, it scans a directory called "BackPlay" under the user's Music directory, and begins playing any music files it finds there in random order. BackPlay is independent from iTunes. It can be paused from an icon in the status area.