The first alpha release of dramatis hit the streets today.

dramatis is a library available in Ruby and Python used to write concurrent
programs based on the actor model of concurrency.

The dramatis web site is http://dramatis.mischance.net

The release is available as a gem on rubyforge at
http://rubyforge.org/projects/dramatis, supports both Ruby and Python, and
comes with API docs, several examples, and a tutorial.