Mendeley is a web-based, free-to-everyone (up to 2 GB of online storage) citaiton management tool supported by Mac, Windows, and Linux. It is also available as a mobile app. For more information, visit the Mendeley website.
Zotero is a free citation management application (supported by Mac, Windows, and Linux). For more information, visit the Zotero website.
OtherOther citation management tools are available, many for free. The University of Wisconsin-Madison has produced a very nice comparison chart of the popular citation management systems. For a very thorough comparison of many free and paid systems, check out Wikipedia.
American Psychological Association guide (used in the social sciences, and sometimes academic papers regardless of subject)
Chicago guide (used mostly in history, fine arts and some social sciences)
Modern Language Association guide (used in the humanities)
Biology
Chemistry
Engineering
Government Documents
