MOC (music on console) is a console audio player with a simple ncurses interface in playmp3list style. It supports MP3 (with ID3 tag, VBR, and Xing headers), Ogg, FLAC, WAVE, Musepack, Speex, WMA, MP4, AAC, and some other less popular audio formats. Playlists can be saved and loaded using .m3u files (PLS version 2 can also be loaded). Internet streams (Shoutcast, Icecast) are supported. It achieves gapless playback by employing an output buffer in a separate thread and file pre-caching. The key mapping can be fully customized. The interface can be detached from the server as it plays in the background.
DeaDBeeF is an audio player for GNU/Linux and other UNIX-like systems. It is written in C with some plugins in C++. It has minimal dependencies, a native GTK2 GUI, cuesheet support, support for MP3, Ogg, FLAC, and APE, chiptune formats with subtunes, song-length databases, and more. It is very fast and lightweight, and extensible using plugins (DSP, GUI, output, input, etc.). The GUI looks similar to Foobar2000.
Music Player Daemon (MPD) is a server that allows remote access for playing music in various formats and managing playlists. It makes a great desktop player with frontend options (Qt, GTK, ncurses, Windows, and Web clients are available). It is also appropriate as a console player that is scriptable, and is especially useful if X is restarted frequently. A set of rapid development tools for clients are being developed and include a C library, Python module, PHP class, Perl module, and Java Class. The goals are to be easy to install and use, to have minimal resource requirements, to be stable and flexible, and easy to interface.
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.
Mp3blaster is an interactive text-based program that plays several audio file types (MP3, Ogg Vorbis, wav, and sid). It is one of the few audio players for the text console that allows full interactive control during playback. One of its key features is the ability to compose a very flexible playlist (while playing!). It plays most MP3 formats and has full mixer support built in.
Mr. Voice is a specific-purpose Perl/Tk front-end for an MP3 database. It was written to provide an easy-to-use MP3 solution for the production booth of an improv comedy troupe, and as such is tailored to providing quick searches and playback of MP3s that are split up into categories. While not intended to be a standalone desktop MP3 player, others in a similar situation may find it useful.