Zotero is a citation management tool that is built into your web browser to help you collect, organize, and share citations. Zotero's big strengths are its browser extensions, which let you grab citations right off the web, and its user-friendly features, like enabling drag-and-drop citation placement. Zotero also helps you create and format bibliographies and footnotes in a wide variety of citation styles. Zotero works with Firefox for PC, Mac, and Linux, and is compatible with MS Office and Open Office. Zotero also has great options for power researchers, like automatically remembering proxies and assigning BibTeX labels based on author name.
You can download Zotero for free here: www.zotero.org.
This video tutorial will give you an overview on how to use Zotero.