zotero

Zotero is a freely available reference management and writing tool that makes capturing citations easy. It has a browser plugin that works in Chrome, Firefox or Safari, and with one click you can add a journal article, Web page, video, or many other resource types to your library.

One of Zotero's strengths is that it is uncomplicated to us, making collaborative projects, especially with people at other institutions, relatively simple via Google Docs.