CBSE Books online

The Central Board of Secondary Education (abbreviated CBSE) is a Board of Education for public and private schools, under the Union Government of India.(http://cbse.nic.in/). CBSE books are available on line now from class I to ClassXII.
http://cbse.nic.in/welcome.htm

These books can be downloaded as Pdf file.You can go to CBSE website to down load these books.
There is one more place where you can download them

http://ncertbooks.prashanthellina.com/