Mychoonz is an MP3 player implemented in AJAX. It allows you to listen and organize your music within your browser, anywhere, anytime, as long as you've got an Internet connection. The idea is similar to projects such as Ampache or Mp3Act, but it focuses more on user interface rather than features.
irrKlang is a high level 2D and 3D cross platform sound engine and audio library that plays WAV, MP3, OGG, MOD, XM, IT, S3M, and other file formats. It can be used by C++ and all .NET languages (C#, Visual Basic.NET, etc.). It has all of the features common to low-level audio libraries as well as lots of useful features like a sophisticated streaming engine, extendable audio reading, single and multi-threading modes, 3D audio emulation for low-end hardware, a plugin system, multiple rolloff models, sound effects, and more. All of these can be accessed via an extremely simple API using an object oriented design.
python_alsaplayer is a set of Python bindings for the alsaplayer libraries. These are intended to provide a minimal level of abstraction over the C libraries. Higher-level abstractions and functionality can then be written purely in Python. This module has dependencies on the boost and Python libraries.
Jam2 is a collection of components for the Drupal 4.7 CMS platform. It provides a number of new node types aimed towards allowing independent musicians to upload media and cover art, add album and artist data, and create and manage podcasts of new material or previously uploaded jams. Uploaded media can be presented to the user as an embedded Flash player, a download link, or both. Users can create podcasts that feature the full array of iTunes tag data, so that podcasts can be easily listed with the iTunes Podcast Directory. Albums, once defined, can also provide their own podcasts, allowing musicians to optionally involve their fans throughout the creation of an album.
Shmplayer executes a single instance of mplayer in the background and controls it through a FIFO. It supports many of the features you'll find in XMMS and it is easily extendible. However, unlike XMMS, shmplayer doesn't require an X server to be active. You can even use it from a remote shell. Shmplayer has also some unique features like "jgrep" that lets you jump to the first "grepped" match of the playlist.