Here is a post about Erlang as "concurrency-oriented programming".
And here about "Erlang vs Haskell comparison"
If you follow the link, some really interesting quotes appear:
Erlang is the specialist language narrowly focused on networked, highly-scalable concurrent applications.
I love Haskell because it forever twisted my brain into a different shape and I think I'm overall a much better coder now.Maybe Io could also have some potential for concurrent programming (futures, coroutines, asyncs). Not at the same scale as erlang, but, who knows...