This list is NOT comprehensive. To get the best databases for your topic:
Academic Search Complete
(Useful for almost every topic of research)
"Academic Search Complete is a multi-disciplinary database, with more than 6,100 full-text periodicals, including more than 5,100 peer-reviewed journals."
(Useful for humanities and biological sciences research)
Access to more than 780 journals in the humanities and biological sciences, especially focusing on journals in botany and ecology. In Advanced Search, you can limit it to types of journals you want to search. JSTOR is also great for art topics.
(Useful for the humanities and social science research)
"Project Muse offers over 250 quality journal titles from 40 scholarly publishers covering the fields of literature and criticism, history, the visual and performing arts, cultural studies, education, political science, gender studies, economics, and many others. Online editions are often available earlier than print editions."
ERIC (at EBSCOhost)
(Useful for Education-related topics)
"The Educational Resources Information Center (ERIC) database covers all aspects of education and educational research. ERIC provides access to education-related resources, including journal and non-journal bibliographic information. Coverage Dates: 1966 – present (though not all articles are full-text)."
MEDLINE with Full Text (at EBSCO)
(Useful for medical and biological sciences research)
"MEDLINE provides authoritative medical information on medicine, nursing, dentistry, veterinary medicine, the health care system, pre-clinical sciences, and much more. Created by the National Library of Medicine, MEDLINE uses MeSH (Medical Subject Headings) indexing with tree, tree hierarchy, subheadings and explosion capabilities to search citations from over 4,800 current biomedical journals."
(Useful for Psychology-related topics)
"PsycINFO, American Psychological Association's (APA) resource for abstracts of scholarly journal articles, book chapters, books, and dissertations, is the largest resource devoted to peer-reviewed literature in behavioral science and mental health. It contains over 2.5 million citations and summaries, and ninety-eight percent of the covered material is peer-reviewed."