Drew Conway and John Myles White have a new book out, Machine Learning for Hackers (ISBN 1449303714). As the name implies, the emphasis is on exploration rather than mathematical theory. Lots of code, no equations.
If you’re looking for a hands-on introduction to machine learning, maybe as a prelude to or complement to a more theoretical text, you’ll enjoy this book. Even if you’re not all that interested in machine learning, you might enjoy the examples, such as how a computer could find patterns in senatorial voting records and twitter networks. And R users will find examples of using advanced language features to solve practical problems.