A Ruby shell in Autodesk Revit using IronRuby.
RevitRubyShell is a Ruby shell in an Autodesk Revit add-in external application.
It enables you to interactively run Ruby scripts inside Revit using the Revit API and IronRuby.
You can build from source and add the add-in manually or using the add-in manager.
There is also an automated installer available here (IE only) or here.
This application is heavily inspired by RevitPythonShell and this article about embedding IronRuby.