Open Scientific Books
"A surprising number of books are beginning to be freely available in electronic form. All of Stephen Wolfram's A New Kind of Science has recently become available online, although requiring free registration. The book is already an amazingly encyclopedic work, but the online version actually augments each page with additional material. It also enhances the book by providing a full search facility. Finally, by making the thousands of images within the book available, researchers can exchange notes on specific parts of the books along with supporting images.
A very popular undergraduate text, Introduction to Probability by Grinstead and Snell, has similarly become available online. They also provide considerable additional material and a complete set of programs are made available in four formats: Mathematica, Maple, Basic, and Java Applets. In addition, the answers to the odd-numbered problems are available, and instructors can get the even ones with an email to the authors. It's striking to read their discussion about how the GNU version of the book will improve over the existing paper version, and about their gratitude to the American Mathematical Society, publisher of the paper version.
Perhaps the most respected introduction to computer science is Abelson and Sussman's Structure and Interpretation of Computer Programs. It also is freely available in electronic form. In this case, the electronic version evolves the book into an entire course. For self study, the book's website includes sample programming assignments, all the source code used in the book, and assistance in obtaining Scheme, the language used by the book." (http://www.backspaces.net/research/opensource/OpenSourceResearch.html)
Wolfram, Stephen. A New Kind of Science (Champaign, IL: Wolfram Media, 2002).
Grimstead, Charles and J. Laurie Snell. Introduction to Probability, 2nd. rev. ed. (Providence, RI: American Mathematical Society, 1997);
Abelson, Harold, Gerald Jay Sussman,.and Julie Sussman. Structure and Interpretation of Computer Programs,2nd ed. (Cambridge, Mass.: MIT Press, 1996).
McKay, David J. C. Information Theory, Inference and Learning Algorithms (Cambridge, U.K.: Cambridge University Press, 2003).