An outstanding recipe book for collective intelligence algorithms that spans the gamit from Pearson’s correlation and Euclidean distance measures to optimization, Bayesian filtering, neural networks, genetic algorithms, and support vector machines. Non-negative matrix factorization is thrown in to keep most of us humble. What makes the book unique is that each algorithm is described intuitively and mathematically AND implemented in practical Python applications. While a fair amount of Python sophistication is assumed, programmers of Java or C++ will have little trouble picking it up.
Toby Segaran, Programming Collective Intelligence: Building Smart Web 2.0 Applications (O’Reilly, 2007).