A rare thing, a discussion between Carl Hewitt (the man who designed the actor model), Erik Meijer and Clemens Szyperski about the concepts behind the actor model. Way more valuable than the hordes of Akka tutorials.
The wikipedia page about the Actor Model is also very knowledgeable on this subject.
For further reading, the original paper can be found online: A Universal Modular Actor Formalism for Artificial Intelligence.
A french online meetup dedicated to non-mainstream technologies, held once a month, and for (I hope) many years to come.
I can’t say enough how I find this initiative awesome, because it can be so hard for non-mainstream enthusiasts to discuss physically about these subjects.
Why would I use something else than the venerables Java or C# in production? Frédéric Menou gives his view (in french) on this subject, and that’s refreshing for the wannabe functional developer I am.