Protocol Buffers - Google's data interchange format
Enjoy Learning.
JRuby, an implementation of Ruby on the JVM
Fibers, Channels and Actors for the JVM
java virtual machine in pure node.js
An alternative to Zend PHP, like JRuby and Jython only for PHP
The Eta Programming Language, a dialect of Haskell on the JVM
Orbit - Virtual actor framework for building distributed systems
Dead-Simple Packaging and Deployment for JVM Apps
Avian is a lightweight virtual machine and class library designed to provide a useful subset of Java's features, suitable for building self-contained applications.
TestNG testing framework
Fibers, Channels and Actors for Clojure