Google Ants[0] is an AI challenge that is over now, unfortunately, but you can still run through it.

"The AI Challenge is all about creating artificial intelligence, whether you are a beginning programmer or an expert. Using one of the easy-to-use starter kits, you will create a computer program (in any language) that controls a colony of ants which fight against other colonies for domination."

[0] http://ants.aichallenge.org/