All the websites below have a plenty of books and papers for free reading & downloading.
The National Academies Press, free reading and downloading in PDF, account needed for downloading.
Australian National University Open Research Library, all materials come from ANU, fill a form to request the PDF copy.
The University of Adelaide > Library > eBooks, free reading and downloading in HTML, epub, and Kindle.
Curtin University Library, free reading and downloading in PDF.
University of Queensland, part free.
Project Gutenberg, the greatest one, no more explianation.
The New Zealand Digital Library, free reading online.
Cornell University Library, free downloading in PDF.