Two free ebooks today.
The first is Breaking the Law of Averages, an introductory statistics book that I recomment. Matt Briggs approaches the subject in a wholly modern way, relying on your computer to do the math, allowing the student to focus on the more important task of understanding what you are doing. Briggs applies objective Bayesian probability theory in this book, allowing for an easy introduction to the subject. This book also has a simple R primer in it.
The second is Modern Perl, a primer on Perl 5.