Modern Language Association (MLA) Handbook
Basic MLA Citations (pdf)
(especially psychology, behavioral science, and education)
American Psychological Association (APA) Publication Manual
Basic APA Citations (pdf)
CSE (Council of Scientific Editors) Manual
Turabian is used by students in all disciplines. It is designed to complement the Chicago Manual of Style, but is simpler and easier to use.
The Chicago Manual of Style is used by scholarly writers in all disciplines.
It contains two separate styles, one for writers in literature, history, and the arts, and one for writers in the physical, natural and social sciences.