Cymbaline is a learning music player. It sets a score for each track based on your listening habits, and you can set thresholds to create playlists with your favorite tracks automatically. In random mode, it will play your favorite tracks more often. It also allows album-based navigation: you can start playing the next album, skip 2 albums ahead, go to a specific album, etc. It has a random queue mode where you see a list of randomly chosen tracks that play consecutively. The queue is also built based on song scores.
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.
extm3u.pl generates an extended .m3u playlist from a given directory. The generated playlist can be used with XMMS, Winamp, and other MPEG layer 3 players. The playlist is printed to stdout. Extended .m3u files contain additional information, such as the length of the song and data from the ID3 tag. This script requires the MP3::Info Perl-module.
rioutil is a utility designed for the use of interfacing with Sonic Blue/dnna's third, fourth, and fifth generations of flash MP3 players (Rio 600/800/900/S-Series/Riot/Cali/Chiba/Fuse and Nike psa[play). On many players, it goes beyond the packaged software by providing downloading.
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.