Zotero (pronounced "zoh-TAIR-oh") is system that collects, manages, and cites research sources.
Zotero allows you to attach PDFs, notes and images to your citations, organize them into collections for different projects, and create bibliographies.
It automatically updates itself periodically to work with new online sources and new bibliographic styles.
If you use Google Chrome or Safari, and Word:
Zotero also works with OpenOffice/LibreOffice/NeoOffice. If you use one of those programs, make sure you install the right plugin -- see http://www.zotero.org/support/word_processor_plugin_installation_for_zotero_2.1
If you use Firefox and Word: