Free data science books

From http://www.p-value.info/2012/11/free-datascience-books.html

I've been impressed in recent months by the number and quality of free datascience/machine learning books available online. I don't mean free as in some guy paid for a PDF version of an O'Reilly book and then posted it online for others to use/steal, but I mean genuine published books with a free online version sanctioned by the publisher. That is, "the publisher has graciously agreed to allow a full, free version of my book to be available on this site." 
Here are a few in my collection:

• Mining of Massive datasets by Rajamaran, Leskovic & Ullman

• Bayesian Reasoning and Machine Learning by David Barber [website]

• Information Theory, Inference, and Learning Algorithms by David J.C. Mackay

• Foundations of Statistical Natural Language Processing by Manning & Schütze

While we are on the subject, I would be remiss of me not to recommend D.J. Patil's free minibooks/essays. While they are not the thick comprehensive tomes of those above, they are definitely worth the time to read. 

• Data Jujitsu by D.J. Patil

• Building Data Science Teams by D.J. Patil

Finally, this is work in progress (just 3 chapters to date) but is one to watch: Network Science by A.-L. Barabasi.
Update [12/27/12]: adding in some additions from a hacker news discussion and the comments below (thanks guys):

• Introduction to Information Retrieval, by Manning, Raghavan and Schütze

• A first encounter with machine learning by Welling

• Gaussian processes for Machine Learning by C.E. Rasmussen

• The Elements of Statistical Learning, by Hastie, Tibshirani, Friedman -- grandaddy of them all

• Introduction to Machine Learning by Smola, Vishwanathan

• Think Bayes by Downey