This has caught a lot of attention over the last couple of weeks. Sun has recruited the two main developers of the JRuby implementation of Ruby on Java, Charles Nutter and Thomas Enebo.
Tim Bray, Director of Web Technologies at Sun, as posted this article on his personal blog that answers some of the questions about this move and the reasons for why Sun is taking an interest in JRuby.
The main reasons given for this move seem to revolve around Sun and the Java communities current interest in supporting and running dynamic languages on the Java platform. Since what Nutter and Enebo have implemented so far is a version of Ruby that runs on the Java platform, this fits well with this current interest, and of course brings the advantages and associated hype of Ruby and of course Ruby on Rails to Java.