Oracle's has release their details of Project Nashorn which will allow JavaScript to be embedded in Java applications and to develop standalone JavaScript applications.

With the ubiquity of JavaScript engine there has been a badly needed refresh and a welcome report of five times speed up on performance than the current Rhino implementation and a much smaller footprint.

Unfortunately the planned release is for Java 8 in late 2013. Hopefully it will be competitive with the planned nodejs 2.