If you have the slightest interest in the issue of concurrency then you should study Erlang and Clojure. Since Moore's Law has largely faded, and we now gain speed by putting more CPUs in each server (rather than having the individual CPUs be faster) concurrency is an increasingly unavoidable aspect of programming. Joe Armstrong (Erlang) and Rich Hickey (Clojure) have both spent an enormous amount of time thinking about how to support concurrency in a programming language. Armstrong talks about a paradigm that he calls "Concurrency Oriented Programming". Armstrong's thesis is surprisingly readable and I recommend it:
http://www.erlang.org/download/armstrong_thesis_2003.pdf
Rich Hickey's video presentation "The value of values" is also a good overview of some concepts that are important to Functional Programming: