* Audacious is a XMMS look-alike written in GTK 2. It supports XMMS skins but does not behave exactly like XMMS. Several plugins are available like audacious-docklet that displays an icon in the systemtray, audtty that allows you to control audacious in the command line, audacious-crossfade that allows continuous output and crossfading and a lot more to come or already available. There is a thread on the forums where you can request plugin ports.
* MPD: Music Player Deamon is another good player which uses a client/server architecture. You can even launch it at start-up and have music playing before you get on your desktop. It has a lot of clients and obviously, there are some that don't require X, like ncmpc which is ncurses-based.
* Amarok: the well-known full-featured player, considered by many as the best player available. Amarok was initially designed for KDE and does almost everything, except dishes.
* Rhythmbox: Rhythmbox plays in the same category as Amarok but is designed for Gnome. Both are comparable to iTunes.
* Banshee: Banshee is also in the category of heavyweight audio players. There are lots of plugins available and under development. It uses Mono.
* Muine: A simple music player for Gnome that runs upon mono framework. It has a simple interface and supports plugins.
* Listen: Listen is promising audio player, also heavyweight. It is also designed for Gnome. It doesn't do dishes either.
* mpg123: Another category here. mpg123 is a CLI player for those of you that do not like graphical interfaces or do not have access to it at the moment.
* Quod Libet: A GTK+2 based music player written in python. It is full featured and even has built-in tag editing. There are a number of plugins available to add additional functionality.