Jacob Kaplan-Moss has published his talk he gave at PyCon Argentina and PyCon Brazil 2009. A really good write-up, I would like to just pick one small part out:

Even worse, tools like WSGI and Rack do nothing to help inter-language inter-operability. I’d really like to write parts of my application in Python, parts in Clojure, parts in Ruby, and even parts in Perl. Things like web proxies, SOA, ROA, and language VMs help, here, but since gateways aren’t APIs there’s only so far we can go.

If you're looking for efficient inter-language interop, I would suggest looking at protocol buffers.