Twitter (Scala) and ITA (Common Lisp) come to mind, and I'm sure a number of startups are using Clojure with Ring, Compojure, or Noir.
If by "production" you mean application domains of software that startups typically write, the more statically-typed functional languages (i.e. those based on Hindley-Milner) like OCaml, SML, and Haskell are seen less frequently because startups are constantly changing their designs and features, and those languages aren't well suited for what pg calls exploratory programming. However, as you pointed out, Jane Street appears to be highly successful with OCaml (although they don't report their earnings), and several well-known FOSS projects like darcs and xmonad are written in Haskell.
Edit: Also, Ruby and Python are probably as well suited to functional programming as Scala is, outside of Scala's parallelization models that we tend to associate with functional programming. And I've certainly seen production code written in Ruby and Python. :)
Interesting stuff, thanks for the info! Looking across the board, I don't see many companies using functional languages (at least they don't advertise it in public) be they startups or megacorps, hence my question.
If by "production" you mean application domains of software that startups typically write, the more statically-typed functional languages (i.e. those based on Hindley-Milner) like OCaml, SML, and Haskell are seen less frequently because startups are constantly changing their designs and features, and those languages aren't well suited for what pg calls exploratory programming. However, as you pointed out, Jane Street appears to be highly successful with OCaml (although they don't report their earnings), and several well-known FOSS projects like darcs and xmonad are written in Haskell.
Edit: Also, Ruby and Python are probably as well suited to functional programming as Scala is, outside of Scala's parallelization models that we tend to associate with functional programming. And I've certainly seen production code written in Ruby and Python. :)