Microsoft XNA Game Studio 2.0

Microsoft XNA Game Studio 2.0 enables hobbyists, academics, and independent game developers to easily create video games for Windows and the Xbox 360 console using optimized cross-platform gaming libraries based on .NET. It supports development in Visual C# 2005 Express Edition and Visual Studio 2005 Standard Edition and higher.

Microsoft XNA Game Studio 2.0 contains improved performance along with new features such as expanded support for Visual Studio 2005 products, networking and multiplayer support, the XNA Game Studio Device Center, easier Xbox 360 connectivity, improved content pipeline experience, and much more.

For additional information, see the following links:

Microsoft XNA Game Studio 2.0 getting started guide
Microsoft XNA Game Studio 2.0 installation instructions
Overview of new features in Microsoft XNA Game Studio 2.0
XNA Creators Club home page
XNA Creators Club forums