For those interested in what programming languages are available on the JVM - yes, there are far more than just Java. And many of them are far more interesting than Java. And many integrate very well with Java libraries. In any case, Robert Tolksdorf has started building such a list here. I have no idea if it's complete, but the selection is enough for me ...
(although of course I'm biased and would only take either a Lisp dialect or Jython anyway)