A friend and colleague of mine is boasting a lot about Clojure and it's productive capabilities. But I really can't wrap my head around the LISP syntax. Perhaps it's a matter of putting in time.
If one want to stay on the awesome JVM with its performance, Scala is worth checking out. It's the language which is said to fuse functional and object-oriented programming in a great package. Read the linked article, "On Scala", for a nice walkthrough.