- XMMS: is a very popular player and has the "look 'n feel" of Winamp. Even Winamp's skins work with it. This one exists in Linux as far as I remember actually using Linux
http://www.xmms.org/
- Amarok: Very popular too. I really like Amarok's interface and many KDE-based distros are shipping with it today.
http://amarok.kde.org/
- Rhythmbox: A great GTK application. Even though I often type its difficult-to-spell name wrong, it's worthy taking a look into it
http://www.rhythmbox.org/
- Mplayer: Not only mp3 player, but capable of playing also mp3 is mplayer:
http://www.mplayerhq.hu/homepage/design7/dload.html
I'm used to love this one... It can play practically everything you can ever think of. But the guys behind this project think they are the Uber-coders and has problems accepting any compiler other then gcc3.x... They also "disagree" with the way DVD's organize the files. Playing DVD's with it can be really problematic, especially if you want subs, menus or playing in other languages. So I've dropped it and moved to:
Xine: A great player in all aspects. It uses the same codecs as mplayer. Unlike mplayer, the gui is very well integrated and it has real support for DVD menus:
http://xinehq.de/
if you don't like it, you can use Totem:
Totem: It's the official Gnome player. It can use gstreamer or xine as the rendering engine. Very well thought interface, it's the player I currently use (totem-xine)
http://www.gnome.org/projects/totem/
When looking for a program in Linux, assuming that you are familiar with Windows, take a look into this table:
http://www.linuxrsp.ru/win-lin-soft/table-eng.html
it will give you a lot of ideas of what to look for.
Regards!