Just in case you don't think Haskell is being used for anything but academics then check out the Commercial Users of Functional Programming site. They have an annual conference as well.

Purely functional programming is a brilliant idea with a misleading name. When people talk about “purely functional programming”, they mean Haskell or something like Haskell. But that’s not ...

For example, JavaScript, Lua, and Perl 6 are scripting languages that support functional programming; C++ 11, C# 3+, and Rust are C-like languages that support functional programming; and MATLAB ...

LISP was the first functional programming language, followed by Erlang, Scheme, Haskell, OCaml, Scala, Clojure, F# and others. Advertisement THIS DEFINITION IS FOR PERSONAL USE ONLY.

Facebook went with a novel programming methodology, called functional programming, to update the News Feed for its Apple iOS client, which helped considerably in tuning and debugging the app.