Zotero: The Tri-College Libraries recommend Zotero, a free online app that can format your bibliography, keep your citations organized, and even save your articles in the cloud so you can access them later from the library, home, or a café.
Guide to Zotero
Tricollege guide for using Zotero. Starts with an introduction and installation before describing how to use if as a versatile tool for research, footnotes and bibliographies.