Guayadeque is starting to become a mature, reliable music player - the latest version 0.2.9, released today brings some very important features to Guayadeque like Ubuntu sound menu support, iPod support with covers and playlist, usb mass storage devices support, support for trueaudio files and wavpack, option to embed album cover to all album tracks, output audio device configuration option in
Audacious is a lightweight music player for Linux (but it seems version 2.5 will work on Windows too) that comes with two interfaces: a GTK interface and a Winamp 2.x-like interface that supports Winamp skins:

CMus is a free, powerful, terminal-based music player using the ncurses toolkit. CMus supports various audio formats, including Ogg Vorbis, FLAC, MP3, WAV, Musepack, WavPack, WMA, AAC and MP4.
Wouldn't it be great if you could tune into your local music like you do with the Last.fm radio? TagPlayer, a new Linux music player does just that: it plays your local music by using its Last.fm tags.
XBMC is a free and open source (GPL) software media player and entertainment hub for digital media for for Linux, OSX, Windows, and the original Xbox.
Clementine gains more and more popularity with its port to KDE4 based upon the Amarok 1.4 player, and the latest version bundles a fair amount of new features. In case you didn’t try it yet, Clementine is a free, cross-platform music player available for Linux, Windows and Mac.
The first Amarok 2.4 beta, codenamed “Closer”, was released just a few days ago, on December 7, and it looks very promising.
We've already covered all the new features in Clementine 0.6 (release candidate at the time) so this post is just a small update to let you know that Clementine 0.6 stable has been released. There are no new features since the RC, only bug fixes.
Clementine, the Qt port of Amarok 1.4 got a huge list of new features in the latest 0.6 release candidate version.
Foobnix, a very interesting music player we wrote about a while back (check out that post for a complete review) has been updated to version 0.2.2 and also it now comes with an Ubuntu PPA.
Your favourite music player is not supported by the new Ubuntu 10.10 sound menu or not using Ubuntu 10.10 Maverick Meerkat yet?
Spotifycmd is a command line tool (which even though is called "spotify_cmd.exe", is actually a Linux binary) that can control a running instance of Spotify (in Wine).
DeadBeef, a lightweight music player I was telling you about in the
Clementine is a port to KDE4 of one of the most beloved music players on Linux, Amarok 1.4. The latest release brings several new features, including iPod, MTP and USB mass storage disks support, queue manager, support for Wii Remote to control it, and numerous bug fixes to already existing features.
Decibel is a music player built in GTK which takes a different approach when it comes to the way features are implemented, and that is, Decibel uses only plug-ins which can be enabled or disabled on demand. This makes it either a pretty featured player, or a very simple and basic one, depending on which plug-ins you need enabled.
Today, a new project has been registered on Launchpad, called Rhythm-e. The project was registered by Ammonky - who's also behind Nautilus Elementary. No code has been published yet (update: the code can be found HERE), but you can get an idea on how it will look:
Clementine 0.5 has been released.