iTunes Export provides the ability to export iTunes Playlists to the standard .m3u file format. Unfortunately, this feature is not included in the iTunes application and is extremely useful for users who wish to use iTunes with other applications or devices. iTunes Export is written in C# (.Net). iTunes Export provides a Command Line version (tested on Mono) and a GUI version, as well as a library that developers can use in their own applications.
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.
MPy3 is a full-featured, modular, configurable MP3 player system aimed at jukeboxes or car MP3 systems. It can play MP3s via rxaudio or mpg123, take input from a keyboard (tty), LIRC, or joystick. It does output through a CrystalFontz LCD directly, or through any LCD that LCDProc supports, or even through X. It features playlist support and support for controlling the mixer (using aumix). All of the inputs, outputs, and other functions are controlled via a number of modular libraries which can be used in other projects as well.
The Java Media Framework (JMF) is an API for incorporating audio, video, and other time-based media into Java applications and applets. It is an optional package that extends the multimedia capabilities on the Java2 platform. The Blackdown JMF is a Performace Pack which includes native code in order to provide faster processing and tighter integration with Linux than the all-Java version.