PHP!

Haskell is an advanced purely-functional programming language. An open-source product of more than twenty years of cutting-edge research, it allows rapid development of robust, concise, correct software. With strong support for integration with other languages, built-in concurrency and parallelism, debuggers, profilers and rich libraries.

Erlang is a general-purpose concurrent, garbage-collected programming language and runtime system used to build massively scalable soft real-time systems with requirements on high availability. The sequential subset of Erlang is a functional language, with eager evaluation, single assignment, and dynamic typing. It was designed by Ericsson to support distributed, fault-tolerant, soft-real-time, non-stop applications. It supports hot swapping, so that code can be changed without stopping a system. »

LiveScript is a language which compiles down to JavaScript. It is a fork of Coco which is in turn derived from CoffeeScript. Like those two it has a relatively straightforward mapping to JavaScript. LiveScript is Coco but much more compatible with CoffeeScript, more functional, and more feature rich. LiveScript aims for increased expressiveness and code beauty.