Microsoft's free DirectX SDK, used to access 3D accelerators, sound cards and input devices through a unified interface. Includes Managed DirectX for .NET 1.1 as well as the new Managed DirectX for .NET 2.0.

Portable .NET bindings for most of the libraries popular in game development, including DevIL, OpenGL, SDL, Cg, ODE and OpenAL. Saves you from the work of writing custom wrappers and updating them on each and every .NET platform, though you will still have to cope with the procedural API these libraries provide.

Purple# is a game engine written in C# from scratch. Besides being a 3D engine, this project also integrates audio playback, input device management and simple GUI capabilities.

C# component that decodes ogg vorbis files into a sound stream. Can be used to portably stream Ogg Vorbis without requiring any external libraries.

Sound library for the Axiom Engine. Integrates into the normal Axiom scene node tree for placeable, automatically update 3D sound sources. Also able to play background noise and music. Can play back Ogg Vorbis files and supports DirectSound as well as OpenAL.

A DirectShow wrapper for .NET that features the full DirectShow interface. Intended as a replacement for Microsoft's AudioVideoPlayback.dll that has been discontinued in Managed DirectX 2.0 without a real alternative being ready to fill the gap.