Everyone researching with electronic sources knows the pains of collecting articles, managing a library, and, worst of all, creating citations. Zotero is a veteran (and completely free) browser add-on that solves nearly all these problems. Originally available only for Firefox, cross-platform tool Zotero has recently become available for Chrome and Safari as well via its standalone desktop version.
Zotero makes it easy to collect research papers off the Web, attach PDFs, find relevant articles in your library, and sync it across PCs. With the help of a Microsoft Word/LibreOffice plugin, Zotero takes the pain out of citations and bibliography, doing all the heavy lifting for you, using any of the major citation styles. It's indispensable for students.
Note: The Download button takes you to the vendor's site, where you can download the edition appropriate to your system.