"Zotero [zoh-TAIR-oh] is a free, easy-to-use Firefox extension to help you collect, manage, and cite your research sources. It lives right where you do your work--in the web browser itself."

The Zotero 1.5 Beta Firefox extension offers a number of new features including online reference storage/synchronization and WebDav functionality, which allows users of, say, Sakai to add files and references directly to a course site via the Zotero interface. Additionally, the extension can be installed and synchronized on a number of machines or via Zotero's new web application, allowing access to your research anywhere. A full list of new features are described on the Zotero website. For an excellent demonstration of what Zotero can do for your research watch the video below.