I'm a big fan of AI, and especially love it when your programs get to compete head to head with ones written by other people. I noticed no one's posted about this site, so I thought I'd bring it up.
HackerRank is basically a platform that allows programmers to compete in collection of intellectually stimulating AI problems. I haven't delved very deep into it yet, but I just wanted to share this cool site with everyone. (And I'm bored of waiting for Google's new AI challenge.)
Here is the site: HackerRank Site