Zotero is a free and open-source bibliographic management tool. It allows you to collect, store, and organize citation information from journal and newspaper articles, books, websites, and more- so that you can create your own personal library. With Zotero you can store up to 300MB of information and collaborate/share with as many people as you like! Zotero works with Firefox, Chrome, and Safari browsers.
The Zotero website offers excellent installation instructions and general documentation.