Predatory journals spam thousands of scientists and other researchers, offering to publish their work for a fee, without actually conducting peer review.
Jeffrey Beall, a librarian at the University of Colorado, kept a list of these illegitimate journal publishers to help researchers avoid being taken in; he was forced to stop in 2017. An archived version of the last update of the list is here.
The Directory of Open Access Journals (DOAJ) is a list of quality, peer reviewed open access journals. DOAJ is co-author to the Principles of Transparency and Best Practice in Scholarly Publishing and journals included are expected to follow these principles. The DOAJ maintains a list of journals that have been accepted into or removed from the DOAJ.
Research on predatory journals from the Centre for Journalology.
Related article: “A paper by Maggie Simpson and Edna Krabappel was accepted by two scientific journals.” Dec. 7, 2014. Details here.