I've been working on a home-grown AI simulation for the past week or so.  The code is posted here:

http://code.google.com/p/kindohm-life/

If I get some free time tonight I'll post some more interesting details about it.  Basically it's an environment with herbivores, carnivores, and plants that carry out their short lives walking, eating, mating, and then dying (usually of starvation - at least up to this point). 

The motivation for this?  Just because.

What have I learned so far?  A little bit about threading (in the user interface), and that adding one variable to your AI increases the complexity exponentially.