Cog is an audio player for Mac OS X written with Cocoa. It supports many popular file formats, including Ogg Vorbis, Flac, Musepack, Mp3, and Monkeys Audio.
Play is an audio player supporting Ogg Vorbis, FLAC, and numerous other audio formats.
GSburn.app is a GNUstep based CD burning program for GNU/Linux. You no longer need to remember ugly command line parameters or write shell scripts. With GSburn.app you compile your CD by point-and-click operation and save your projects for later reuse.
A fast, extensible, open-source iTunes alternative written in Cocoa. Uses native Mac OS X widgets, features a "skinnable" mini-mode, and is compatible with Mac OS X themes and ShapeShifter AppSkins.
mytunes - A sweet mp3 (and later other formats) player, made to be used in a GNUstep, or other OpenStep/NeXTSTEP/Cocoa-like environments. Offers wonderous playlist support, including superlists, which are similar to smart lists.
qtplay is a lightweight command-line audio player for OS X that handles CDs and local and network file formats supported by Quicktime. It displays ID3 tags, and can log track information to last.fm.