Open-access literature is digital literature that is available on the web, free of charge, and free of most copyright and licensing restrictions. Committing to open access requires dispensing with the financial, technical and legal barriers that are designed to limit access to scientific research articles to paying customers. The only constraint on reproduction and distribution, and the only role for copyright in this domain, shoold be to give authors control over the integrity of their work and the right to be properly acknowledged and cited.
Listed below you will find a directory of some of the major Open Access collections available on the web.  

1. AGRIS
   AGRIS is the international information system for the agricoltural sciences and technology. It was created by the Food and Agricolture Organization of the United Nations (FAO) in 1974, to facilitate information exchange and to bring together world literature dealing with all aspects of agricolture.
2. AGRICOLA
   AGRICOLA (AGRIColtural OnLine Access) is a bibliographic database of citations to the agricoltural literature created by the National Agricoltural Library and its co-operators. Production of these records in electronic form began in 1970, but the database covers materials in all formats, including printed works from the 15th century. Coverage: 1978-present. 
3. Algebraic & Geometric Topology
   AGT is a folly refereed journal covering all of topology, understood broadly. AGT is published in free electronic format by Geometry and Topology Publications, with papers appearing a few days after acceptance. AGT is freely available online to all users. 
4. American Medical Association (AMA)
   The American Medical Association provides ten scientific journals without charge to developing nations. The titles include The Journal of the American Medical Association (JAMA); Archives of Dermatology; Archives of Facial Plastic Surgery; Archives of General Psychiatry; Archives of Internal Medicine; Archives of Neurology; Archives of Ophthalmology; Archives of Otolaryngology--Head and Neck Surgery; Archives of Pediatrics and Adolescent Medicine and Archives of Surgery.
5. Analytical Chemistry Web Resources
   A compilation of resources (by Ghirma Moges) usefol to support teaching and research in the field of analytical chemistry, including technical and specialized databases, encyclopedias and dictionaries, journals, university departments, organizations, societies, chemical companies and manufacturers, news sources, and much more. There is also a special section devoted to 'Chemistry in Africa ' with links to educational and research materials, online textbooks, and other tools and resources for students.
6. ArXiv
   Ground-breaking pre-print server in selected physics, computer science, maths and neuroscience disciplines. Contains 100,000's articles submitted by members of the user community. Free access to all papers to all users . 
7. Association for Information Systems
   All university libraries in countries listed in the World Bank's list of high income economies can be granted free subscriptions to the high-quality electronic journals Communications of AIS and the Journal of AIS . 
8. Behavioral and Brain Sciences
   Totally open archive journal where users can submit papers, commentaries, responses and search the archive for papers in all fields of the Brain/Behavioral Sciences. Access to all articles is free to all users. 
9. Berkeley Electronic Press (bepress)
   The Berkeley Electronic Press (bepress) makes its current journals freely available to researchers in the developing world 
10. Best of Science
    The Best of Science is a free-access scientific publication of preprints and peer-reviewed articles. It is publishing in five major fields split in thousands of special areas: Exact Sciences, Technologies, Biological Sciences, Medical Sciences and Human Sciences. Best of Science authors pay for the publishing process of papers and preprints. Fees are low and especially adapted to respond to the geographical origins of the authors. Papers can be published 1 week after reception. Access to the journal is wholly free. 
11. Biblioteca Virtual de Ciencias Sociales de América Latina y el Caribe
    An initiative of the Latin American Council of Social Sciences (Consejo Latinoamericano de Ciencias Sociales, CLACSO) providing free access to 1,800 foll-text books, periodical articles, conference proceeding and also to databases with information about publications, research projects and researchers working in its network of 130 social science research institutions in 19 countries of Latin America and the Caribbean. 
12. Biogate
    Compiled by staff at the Library of Ecology, the National Resource Library of Biological Sciences at Lund University in Sweden , this is a portal to "our 1,000 best links in the biological sciences." Search, or browse by 11 broad subject categories in the biological sciences, which are divided into sub-groups showing the number of links for each. 
13. Bioline International
    Bioline International is a not-for-profit electronic publishing service committed to providing access to quality research journals published in developing countries. Explicit goal of reducing the South to North knowledge gap. Publishes in the following areas: health (tropical medicine, infectious diseases, epidemiology, emerging new diseases), biodiversity, the environment, conservation and international development. Features 18 peer-reviewed journals from Brazil , Cuba , India , Indonesia , Kenya , South Africa , Uganda , Zimbabwe . Many journals are available free of charge.
14. BioMed Central
    BioMed Central offers online publishing of articles in all areas of original biomedical research with foll peer review and open access. Submission is online and authors retain copyright. All original articles are published in one of the BioMed Central journals (18 in the field of Biology and 52 in the field of Medicine), as well as being posted without delay on PubMed Central and indexed in PubMed. 
15. BMJ Journals
    Free access to the electronic version of the British Medical Journal Publishing Group's 28 specialist journals now including Evidence-based journals. These are freely accessible to anybody in the 100 poorest countries in the world. Users shoold follow the standard subscription procedure as the BMJ subscription system will automatically recognize the origin of access. 
16. Cancer.gov
    Free to search Abstract database from the US National Cancer Institute. 
17. CERN
    Over 550,000 bibliographic records, including 220,000 foll text documents, of interest to people working in particle physics and related areas. C