Zotero is an easy to use, free, open-source citation management program with a browser version and a desktop version. The browser version works with Firefox, Chrome, and Safari, and syncs to the desktop version. Zotero works well with library databases, Google Scholar, and websites. You can also download a plugin to "cite while you write" in Word and save PDFs of articles as attachments. You get 300 MG of free storage, and can purchase more space if you need it.
Citation organizers (or reference managers) store and organize citation information for a variety of research resources for easy representation in a variety of citation styles. These programs allow you to build reference library for many information sources, including journal articles, books and book chapters, audiovisual materials, websites, and more.