The Delta Engine Public Beta Preview v0.9.0 has just been released. Grab your copy at http://DeltaEngine.net/Download
The Delta Engine allows you to develop applications and especially games for all major AppStore platforms completely under Windows with .NET by using your favorite tools. It is free to use (on Windows, see Licensing), Open Source and written in 100% .NET.
The Delta Engine currently supports Windows, iPad, iPhone, Android, Android Tablets, Windows Phone 7, Xbox 360, Linux, MacOS, the Web as well as more platforms in the future. To use non-windows platforms you will need a license (http://DeltaEngine.net/Licensing
starts with v0.9.1 soon). In v0.9.0 you can already preview the build process and content generation with the Launcher and ContentManager tools.
We are still early in beta, but have been feature complete for a year now to allow writing both simple (see Tutorials) and complex games (see Showcases). We are always focused on making the game developers life easier and we listen to your feedback! Also note that we are currently a programmer focused engine (on purpose), our tools are not artist focused yet.