Textbooks



physics textbook Ben Crowell is a physics lecturer at Fullerton College in southern California after having earned a PhD from Yale University.He must have been born with an extra battery compared to most of us as he beside teaching also write  textbooks, and extremely generous he has given a nice illustrated book on physics free to download from his Conceptual Physics home page.Thanks a lot.
calculus textbook
Another free book published by Ben Crowell under a Creative Commons License to be downloaded from his Calculus home page, complete with source code.The book is intended for self study and will tie in with the open source YACAS computer algebra system, I guess the upcoming GeoGebra 4.2 algebra software will complement this textbook as well.
chemical principles
From the open digital archives at the California Institute of Technology a 1979 chemistry textbook generous are free for download.Thank you. 

Dickerson, Richard E. and Gray, Harry B. and Haight, Gilbert P (1979) Chemical principles. Third edition. The Benjamin/Cummings Publishing Company