Erlang and other languages running on Beam VM (Elixir, LFE, etc.)

Akka, akka.net... Erlang/OTP.

I know of Orbit (Java) and Proto.Actor (Go and .NET)

https://github.com/orbit/orbit

http://proto.actor

These are distributed virtual actor systems, which is the pattern of Orleans. Of course there are many "normal" distributed actor systems (the Erlang Actor model).

Akka for .NET, Java, Scala. BTW Akka is the "A" in SMACK

Celluloid for Ruby.