Back in the day before I ran out of XP activations (stupid thing kept crashing), I used to LOVE Winamp for managing and playing my MP3 collection. It was just so quick, minimal and responsive compared to more management-based programs like iTunes. Imagine my delight when I switched to Linux and discovered XMMS. It was love until the honeymoon stage wore off, and became annoyed by the ugly GTK1 menus and fonts, and the lack of development.
Enter Audacious, a fork of the similarly-fated Beep Media Player. It works with Winamp Classic skins, satisfying my inner Microsoft fanboy. It can play back MP3 plus a slew of other formats. It's got a little bit of effects processing, some Last.FM support, and a whole lot of visualization plugins (like Paranormal!). Install this player, young grasshopper, and go terrorize ShoutCast with your listenership.