[vorg]

Clojure and Scala are really the only alternative JVM languages to gain any traction since Sun/Oracle started promoting the JVM for languages other than Java.

Most of the other languages I've noticed mentioned in the comments so far (i.e. C, C++, Go, Ruby, Python, JavaScript, Haskell) don't target the JVM, and those that do just do it on the side.

Perhaps Ceylon or Kotlin will gain some traction and become a third alternative for the JVM -- all the other contenders have been around too long and lost momentum. I'd pick Kotlin over Ceylon since it can use the popular IntelliJ as a delivery platform.