I have a background in PHP/Ruby/Javascript but also have some experience with Java, Haskell, C and a few others.
I've come to the conclusion that I need to specialize in at least one statically typed language in order to increase my value to potential employers.
It seems like there's a move towards functional programming in the "enterprise" world with the likes of Scala, F# and C# coming to the fore.
My question is what statically typed language will add most to my resume over the next 5 - 10 years. I'm not talking about a basic understanding/knowledge - I can pick that up pretty quickly. I'm talking about investing a substantial amount of time in really gaining some expertise in one of them. Which one should it be?