Zotero
"Zotero is the only research tool that automatically senses content in your web browser, allowing you to add it to your personal library with a single click. Whether you're searching for a preprint on arXiv.org, a journal article from JSTOR, a news story from the New York Times, or a book from your university library catalog, Zotero has you covered with support for thousands of sites. Whether you need to create footnotes, endnotes, in-text citations, or bibliographies, Zotero will do all the dirty work for you, leaving you free to focus on your writing. Create citations in Word and OpenOffice without ever leaving your word processor and add references to an email, a Google Doc, or some other editor simply by dragging one or more references out of Zotero."