Avida is an auto-adaptive genetic system designed primarily for use as a platform in Digital or Artificial Life research. In lay terms, Avida is a digital world in which self-replicating computer programs mutate and evolve. Avida allows the user to study questions and perform experiments in evolutionary dynamics and theoretical biology that are intractable in real biological systems.
Find Avida at: http://devolab.cse.msu.edu/software/avida/