An easily extend-able 2D game engine written in C# with XNA 4.0 for Windows and Xbox 360. Includes level editor and powerful node-based scripting language.
Jemgine features
To get the editor running, follow the directions in
this blog post. Don't forget that you will need a Full XNA Game Studio 4.0 install. The pipeline assemblies are not in the redistributable. For details, read the XNA 4.0 section at
http://forums.create.msdn.com/forums/p/1988/9924.aspx#9924
It's probably a good idea to read all the entries starting
with this one. They will give you a good overview of how the engine works and how to build maps for it.