Zotero - Collect, Organize, Cite, and Share References  

Zotero, is a no-cost bibliographic management tool that runs on the Windows, Mac X, and Linux operating systems. Zotero can: 1) organize references in multiple folders; 2) store references and files on Zotero's web site; 3) format in-text citations and post-text references according to many bibliographic styles; 4) display references on a public web page; and 5) import metadata from library subscription databases and public web sites. 

Setting up a free Zotero account gives you:

1.  unlimited storage space on Zotero’s servers for your metadata (information about your sources, e.g., author, title,   publisher, etc., including your text notes);

2.  up to 300 MB of storage on Zotero’s servers for PDF and image files. You can purchase more file storage space--$20/year for 2 GB, $60/year for 6 GB.

You can choose to just store your source metadata on the Zotero servers and NOT store any files there.

On any computer where you install desktop Zotero, you can configure Zotero to sync your desktop data (and files, if you choose) with the content stored on Zotero’s servers.

Downloading and installing Zotero for Firefox
and
Downloading and installing Zotero Standalone
(Works with Google Chrome and Safari. Also requires you to download/install Zotero Connector plugins for Chrome and Safari):

http://www.zotero.org/download/

Zotero Bookmarklet:
(Desktop, iPhone/iPad, Chrome for Android, Android Browser, Firefox Mobile Browser, Opera Mobile/Mini)

Without installing the Zotero software, you can save items to your Zotero library on the Zotero servers using mobile devices as well as browsers not supported by the Zotero software, e.g., Internet Explorer.

1. Register for a free Zotero account
2. Follow Zotero Bookmarklet installation instructions

Screencast Tutorials from Zotero.org:

http://www.zotero.org/support/screencast_tutorials

Documentation from Zotero.org:

http://www.zotero.org/support/

Mastering Zotero: A User Guide for the Zotero Reference Manager (Sebastian Karcher and Rintze M. Zelle)

http://zotero-manual.github.io/zotero-manual/

Mastering Zotero will be a comprehensive user guide for the Zotero reference manager. Writing has just started, and entries on many topics still need to be written.

Jason Puckett, a librarian at Georgia State University, wrote a book about Zotero and created the following research guide which organizes a lot of useful information:

http://research.library.gsu.edu/zotero