Zotero is a tool that can help you build a personal library of source information from articles, books, documents, web pages, and more. This personal library of sources can work with your word processing tool to format a paper in your choice of style.
Zotero is an extension for the Firefox web-browser (or can be downloaded for the Chrome or Safari connector) that runs in its own pane, separately from web pages. It automatically detects content in your web browser, allowing you to add to your personal library with a single click.
Version 6 of Zotero was released in March 2022. For more information on the new features -- including an upgrade to the notes editor, PDF annotations, and the ability to add notes and annotations directly into your word processor documents -- please see the update post on the Zotero blog:
ZoteroBib is a new online tool from the makers of Zotero, similar to EasyBib or BibMe, that quickly formats citations for your bibliography. You can type in a title to search for a citation, or paste in a URL, DOI, ISBN, or PubMed or arXiv ID. ZoteroBib will then give you a citation in the style of your choice, ready to copy and paste into your document.