[ggchappell]

First of all, I'd work on your list. While it's pretty clear what "functional programming" is, the definition of "functional language" is a bit more vague. Still, everyone agrees that Haskell is a functional language. Also, just about everyone agrees that Python and Ruby, while offering some support for functional programming, can hardly be considered functional languages.

When people talk about "functional languages", they mean things like Haskell, OCaml & other ML-ish languages, Scala, F#, and the various dialects of Lisp (EDIT: and, yes, Rust).

If you really want to expand/change the way you think, then I'd say Haskell is what you want. As for libraries, there is a huge amount of work going into Haskell libraries & bindings for existing libraries. I'm not really able to judge whether any of this work is any good, however.

Scala and Clojure (Lisp dialect) have also been getting a lot of attention lately. They both run on the JVM, and so should have excellent library support.

[jamesbritt]

Also, just about everyone agrees that Python and Ruby, while offering some support for functional programming, can hardly be considered functional languages.

Wait to see how many people here suggest Ruby or Python, or JavaScript, though.