There have been a few bridging projects in the past that aimed at using .NET libraries from Ruby. Now, this is different, this is an actual implementation of the Ruby language for the .NET Common Language Runtime. Seeing how .NET finally seems to be more than OK with dynamic languages (see the amazing IronPython project), this could prove to be a very interesting turn of events. The open-source project, initiated by the Queensland University of Technology in Australia, is in its early phases with only some of the standard Ruby libraries implemented. This is not very surprising as the most difficult parts of porting a language is usually that the language itself is not enough, you also need its base class library if you need more than a familiar syntax and if you want that to have more than marginal usefulness. J# suffers from the same kind of problem with its class library.
Anyway, I thought I'd let you know. Check it out: