This is a Ruby implementation of the very simple Gender Guesser by Dr. Neal Krawetz.
It is limited in efficacy and quite useful if you're getting anonymous mail from an admirer. Agreeing to meet before analysis of the emails could be disastrous.
sudo gem install genders
require 'genders'
analysis = Genders::Formal.analyze("This is a test")
puts analysis.gender
puts analysis.percentage # how much of the text was in the gender's class