Download Zotero and associated plug-ins using these links:
Zotero is a free, easy-to-use Firefox add-on (also supported in other web browsers) that helps you collect, manage, cite and share sources. Designed to be intuitive and unobtrusive (it looks like an iTunes library), Zotero is a powerful tool for academics.
Quickly download the Zotero Firefox Add-on:
Zotero supports research projects large and small from any computer. Since it is web-based and uses your Firefox profile to store your data, it's easy to sync your entire Zotero library to any computer with an Internet connection and Firefox as a browser option.
You can use Zotero for collecting snapshots of the web, as you might a bookmark. The nice thing about Zotero is that it's there when you need it and hidden when you don't.
Since Zotero works from within your Firefox web broswer, you can use Zotero with any operating system: Windows, Mac, or Linux.
Advances on the Zotero Everywhere project has given way to Standalone Zotero 3.0 Beta which allows you to use Zotero with browsers other than Firefox (currently Chrome, Safari; Internet Explorer is in the works).
Zotero has also overhauled their web interface and you can now edit and collect sources through your Zotero.org webpage. This functionality works great and allows users to sync collections to the cloud and access them with any browser, any time.