International Journal of Integrated Care has been open-access through the DOAJ since 2003.
Journal of Workplace Behavioral Health makes many articles available via open access.
New England Journal of Medicine is open access after a six-month embargo has passed. That means if an article is six months older than today's date, it is available as an open-access item on the NEJM website.
SpringerOpen includes a portfolio of 160+ peer-reviewed, fully open-access journals across all areas of science. Open-Access books are included.
BioMed Central publishes 289 open-access, peer-reviewed journals. Be sure to check out the "Browse by Subject" tab under "Journals" for a complete listing of medical subjects.
Open Access is the free, immediate, online availability of research articles, coupled with the rights to use these articles fully in the digital environment. Authors can choose to publish their articles in a growing number of journals that meet the full definition of Open Access. Articles are free to all interested readers, and the publishers place no financial or copyright barriers between the reader and the article.
To learn more about Open Access:
Open Access Explained: YouTube Video
Open Access Fact Sheet, compliments of SPARC: The Scholarly Publishing and Academic Resources Coalition
In addition to looking for journal articles in the CORE databases, you can also find journal articles through open access. Open access literature is digital, online, free of charge and is free of most copyright and licensing restrictions.
The Directory of Open Access Journals includes over 2600 free, full-text, quality-controlled scientific and scholarly journals. The scope includes all subjects and languages.
For best results, click on "Browse Subjects" and choose the area that interests you.
Wiley Open Access is a program of fully open access journals. All research articles published in Wiley Open Access journals are immediately freely available to read, download and share.
Elsevier Open Access offers an open access option to over 1500 established peer-reviewed journals.
Taylor & Francis Open: Taylor & Francis and Routledge currently publish a number of pure open access journals. All of the articles in these journals are published open access. The articles in these journals receive both rigorous peer-review and expedited online publication.
It sounds like an advertisement, but Free Medical Journals is just what it says -- a list of 4800+ free medical journals. You may search by subject, or it lists the top medical journals, in order, and includes information about how far holdings go back and whether there is an embargo.
Science Direct lists many open-access journals, which can be filtered by "Health Sciences" to see all that pertain to the medical field.