A friend of mine pointed out Disco, a map-reduce framework written in Erlang and using Python for writing the actual map and reduction functions. I haven't tried it just yet, but the concept is interesting in that it uses both Erlang and Python.
For the time being, I'm glad there are projects like Disco that are taking multi-language systems seriously and doing interesting work outside the web space. Web developers have been required to deal with different languages whereas a tool like Disco was able to make a conscious decision to use both Python and Erlang. I cannot imagine that the required hetereogenious environment of the web has been critical in exposing the reality that managing multi-language complexity is doable and potentially advantageous.