nRake, the premier project and build template for .NET projects using the Rake build system now has a branch for .NET4 using IronRuby. Projects are also updated to VS2010 format, and Albacore gems are now updated to 0.1.5.
Check out the IronRuby .NET 4 branch of nRake.
or the check out the IronRuby .NET 2 / 3.5 branch of nRake.
Master branch is still using MRI ruby 1.9. However, plans are to change over to IronRuby for master branch in the future. IronRuby is now performing well enough and sufficiently compatible to support .NET builds. IronRuby has advantages around size (smaller download) and more exciting interop possibilities with .NET code.