External Links

You can search these free online libraries if copyright/publication date is not of much concern

Online Books Listing over 2 million free books on the Web http://onlinebooks.library.upenn.edu/

Cornell University Library Open access to 1,202,640 e-prints in Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics http://www.arxiv.org/
Project Gutenberg Project Gutenberg offers over 53,000 free ebooks: choose among free epub books, free kindle books, download them or read them online. http://www.gutenberg.org/
Open Library Open Library is an open, editable library catalog, building towards a web page for every book ever published. http://www.openlibrary.org/