Found a nice video of someone implementing Tic Tac Toe in Clojure, complete with an AI opponent.
I learned quite a bit watching it. Enjoy!
Looks good 
Added it to my “watch this later” list.
There is also similar one in haskell by the same author: http://www.youtube.com/watch?v=P0_rIm9ntiQ
And some comments to katas: http://blog.8thlight.com/chong-kim/2013/09/26/using-katas-to-improve.html
8th light blogs inspired me to do programming katas regularly.