Zotero is a free Firefox add-on and standalone program that will store, manage, and help organize your citations. Its format is similar to iTunes, and it allows users to pull citation information from the web as well as from databases.
You can use Zotero as either its Firefox incarnation, its standalone program, or both.
The standalone program works with Firefox, Chrome, and Safari. You can install Zotero standalone if you prefer for your references to live on your computer rather than on your browser.
Learn to use Zotero by watching Zotero Tutorials.