Science books online

• The digital library
  Along with science related books this site has books on other subjcts such as history, philosophy, music, arts etc. The site has more than 35000 English works that are free for personal, noncommercial use.
• The net library
  Has eContent database for ebooks, eAudioBooks etc.
• Project Gutenburg
  One of the most popular site for downloading books. It has huge database with over 100,000 titles of which around 28,000 books are free to download.
• Online Books on Medical Science
  eMedicine is accessible point of care medical reference available to physicians and other health care professionals on the Internet. Has large number of articles that undergo several levels of physician peer review plus an additional review by a PharmD prior to publication. Also it provides latest news related to medical field.
• The Open Education Database
  Huge resource of online books, video lectures, and course material, etc. that are very useful for students.