i read about
avida in discover yesterday. it is essentially a program these guys wrote to simulate natural selection and evolution using self-replicating computer programs whose "dna" is their list of instructions and how they get used, much like our dna controls the expression of genes and the creation of proteins and amino acids and such.
last night i downloaded it from their website and spent like 5 hours playing with it. i studied genetic algorithms as part of an artificial intelligence class i took at rice, and they have fascinated me ever since, but things have come a long way since then. i often think about working on a project like that, how i would do it, what sort of problems i would try to solve, etc., but i don't think i really have that kind of time or passion for it.