MLA (Modern Language Association) is used by researchers in English and Languages. It is also the most popular general citation style at the College of Charleston.
History is the main department using the Chicago Manual of Style. It should be noted Turabian is an undergraduate version of the Chicago Manual.
These are both good sites offering not only citation examples, but also, inserting parenthetical references properly.
Two disciplines consistently use the APA Style--Psychology (!) and Education.