Last night I watched Nova's Smartest Machine on Earth program.
Really fascinating stuff as it explored how machine learning happens (it is essentially a weighted relevance ranking dependent upon data and rules, but then it makes decision based upon specific bits of information including pattern seeking). It also touched on what makes us human, our peopleness and how our experiences shape our knowledge (and how do you teach those to a computer?) The main focus was exploring the work on the machine Watson which plays on Jeopardy Feb. 14-16. (an overview of how he did on Feb 14)
One interesting example talked about typography and trying to teach a computer to recognize all of the variations of the letter A: from typewritten to handwritten, all of the various fonts... really interesting.