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.
duke is a curses based frontend integrated into the latest version of mpg123. It was written because of the need of a textbased player for playing from a remote computer with telnet or even a text-terminal. It allows you to navigate through directories, add files or whole directories to the playlist, sort, search, randomize select and delete from it. It also parses ID3-tags, shows songlengths and has limited mouse-support.
mp3album.pl is a tool to automatically create album lists from a batch of mp3 files including ID3v1, ID3v2.2 or ID3v2.3 information. It includes logic to split up all files in one directory into separate albums and generates a report file for each album. The reports are customizable through templates and can contain any information found in the ID3 tags. mp3album.pl lends itself very handy when creating an index of a directory containing several albums of music. As Perl currently lacks 'good' Unicode support, the Unicode strings in ID3v2.3 are not yet supported.
BeatPacker is a simple Python script that uses an M3U playlist to generate a temporary folder filled with files that can be easily transferred to a portable music player. It's designed to be used as a target for drag-and-drop, a nautilus-scripts right-click action, or similar purposes. A Windows installer is available.
Playlist Warlock is a text-based frontend for mpg123 written in Perl. It is intended to provide users with the playlist browsing and song selection of a GUI MP3 player from any terminal. It provides a combination of Winamp/XMMS, vi/less, and Unix prompt-style commands for creating, editing, sorting, and navigating MP3 playlists. Using mpg123 as a backend, PLWarlock allows the user to easily browse playlists and play MP3s. It supports contiguous and random play, simple jump-to-song syntax, sorting by filename/path+filename, and all the other commands you've come to expect from a good MP3 player.