Bruce Tate gave a talk on "Languages and Leverage: The impact of programming languages on high-leverage programming". I'm a big fan of Bruce since he wrote Beyond Java, Bruce has been willing to move on to new technologies after making a huge investment in Java.
Bruce took old movies and identified each one with a language making the time more fun.
My random notes (which may or may not be what Bruce actually said):
Complexity is expensive; oversimplification leads to complexity.
Scala is good for java developers to come to the functional party, but perhaps not a good language for those not vested in java.
Lisp is the most powerful language with possible exception of Haskel.
Every 3-5 years Lisp makes a comeback.
The language matters a lot in a project, especially since it affects communication with team members. The community around a language matters.
Bruce uses RubyOnRails for his company.
Don't put in more languages on a whim, make sure adding a new language buys more than the overhead it costs.
Every 10-15 years programming goes through a paradigm shift - we are starting the transition to functional programming to take advantage of all those cores that Intel gifts us.