Here is a list of 65 Math books available online for free, compiled by George Cain of Georgia Institute of Technology. Including really interesting ones such as:
- Algorithms and Complexity by Professor Wilf
- A = B, by Marko Petkovsek, Herbert Wilf, and Doron Zeilberger
- A Course In Algebraic Number Theory by Professor Ash
- Calculus Without Limits, by John C. Sparks
- Handbook of Applied Cryptography, by Alfred J. Menezes , Paul C. van Oorschot, and Scott A. Vanstone
- Graph Theory, by Reinhard Diestel
- Basic Concepts of Mathematics, by Elias Zakon
- An Introduction to the Theory of Numbers by Leo Moser
- Graph Theory with Applications, by J. A. Bondy and U. S. R. Murty
- Information Theory, Inference, and Learning Algorithms, by David J. C. MacKay
- Voting, Arbitration, and Fair Division: The Mathematics of Social Choice by Professor Pivato
- Numerical Methods and Analysis for Engineers, by Douglas Wilhelm Harder
[Via reddit.com: programming]
Also, "comprehensive mathematics for computer scientists" - very good printed book, with a nice online version: http://www.ifi.unizh.ch/math/bmwcs/
-they have live examples using Java. finally a use for applets.