Nightingale is a free, open-source music management program that is based on the Songbird media player source code. It has a slick and user-friendly interface that can be customized with 'feathers', Nightingale's answer to skins.
Thanks to the built-in browser, it is quick and easy to get extra content for the app such as album artwork, add-ons and skins. You can also get extra funcionality via plugins like Last.fm and Icecast support.
Plugins compatible with Songbird (with any modification to the addon)
Multi-platform compatibility with Windows XP, Vista, 7, Linux and Mac OS X v10.5 (x86, x86-64).
Ability to play multiple audio formats, such as MP3, AAC, Ogg Vorbis, FLAC, Apple Lossless and WMA
Ability to play Apple FairPlay-encoded audio on Windows and Mac platforms via hooks into QuickTime (authorization takes place in iTunes)
Ability to play Windows Media DRM audio on Windows platforms
Media files stored on pages viewed in the browser show up as playable files in Nightingale
MP3 file download
Ability to subscribe to MP3 blogs as playlists
Ability to build custom mixes
Ability to scan the user's computer for all audio files and add them to a local library
A configurable and collapsible graphical user interface similar to iTunes, and mini-player mode
Keyboard shortcuts and media keyboard support
Last.fm integration via a plugin, complete with love/hate buttons