BioMed Central 

Collection of over 180 peer-reviewed, open access medical journals.

BMJ Open

An open access, online-only general medical journal dedicated to publishing research from all disciplines and therapeutic areas.

National Academies Press

Freely available collection of reports issued by the U.S. National Academy of Sciences, the National Academy of Engineering, the Institute of Medicine, and the National Research Council. The NAP publishes on a wide range of topics in science, engineering, and health. Many titles are in digital PDF format.

Networked Digital Library of Theses snd Dissertations (NDLTD)

Free access to the abstracts and full text of many theses, mainly from USA and Canada but also from other countries. Searchable.

NISCAIR Online Periodicals Repository

Freely available full text articles from journals published by the National Institute of Science Communication and Information Resources (India).

PubMed Central

A free archive of life sciences journals.