Zotero is a free, open-source reference manager that helps you collect, organize, and analyze sources for your research and share them in various ways. It allows you to:
Zotero interacts seamlessly with most online resources: when it senses you are viewing an ebook, article, website, or other online resource, it can automatically extract and save complete bibliographic references. Zotero effortlessly transmits information to and from other web services and applications, and it runs both as a web service and offline on your personal devices.
The Zotero documentation page provides more detail on using Zotero, including tons of customization options.
If you have trouble with installation, follow these steps: