Mahout: Scaleable Data Mining for Everybody by Ted Dunning.
Has to be the most entertaining and accessible presentations on classification I have seen to date.
Ted is a co-author of Mahout in Action with Sean Owen, Robin Anil, and Ellen Friedman.
If they had more of this sort of thing during the pledge drives to support public television I would bet that their numbers would be better. At least among a certain crowd! 😉