A game framework written with osu! in mind.
One framework for creating powerful cross-platform games
Molecular viewer and prototyping framework
Vivid3D is an open-source 3D engine with powerful 2D UI.
Small lightweight program to customize your keyboard
Modern 3D engine and IDE written using C# and C++.
Mad Vandal's FortressCraft Mod Source Code
Portable game engine with main focus on point-and-click adventures
3D .NET engine for Windows, Linux, Mac
Gives agents personality, moods, emotions and emotional attachments.
XNA based game engine completely written in c#
A cross-platform game framework based on OpenGL and GObject.
GameWizzard is a Sprite editor.
An open source skateboard games engine written in C# and .NET.
Open Source Virtual World and MMOG Development Platform
I am working on upgrading the XNA Platform Game Template.
Investigo - DX9 Performance and Debugging Toolkit
DREAM is an Open Source GCS