Scala
Twitter adapted this language for their backend processing due to performance reasons (the interface still uses Ruby on Rails), IDEA supports it via a plugin, there is already some literature available...
Links:
artima.com: Twitter on Scala (http://www.artima.com)
Martin Odersky: Programming in Scala (Amazon) (http://www.amazon.de)
The Scala Programming Language (http://www.scala-lang.org)
artima.com: Twitter on Scala (http://www.artima.com)
Martin Odersky: Programming in Scala (Amazon) (http://www.amazon.de)
The Scala Programming Language (http://www.scala-lang.org)