Ruby Editor as Visual Studio Shell
as you might know you can use Visual Studio as a base for your own dev tools. You can find more on this here http://msdn2.microsoft.com/de-de/vsx2008/products/default(en-us).aspx
One option is the pure shell. Here Visual Studio is just the base library and editor and stuff. Now Sapphire Steel Software is using the shell to build a Ruby IDE on it. See here http://www.sapphiresteel.com/Ruby-In-Steel-Text-Edition for details. They even have a PE (=Personal Edition) free to use for personal, educational or even commercial use.
Hey, the Microsoft stack is getting Ruby (or Ruby is getting the Microsoft stack)...