Zotero is available via web, firefox extension, and new standalone desktop version. This short guide contains the best features of each.
Zotero Firefox Extension
Zotero detects when you are looking at an article in a database, the New York Times, a book in the library catalog or at Amazon.com. Click on the icon to add to your library.
You can manually add items using the green plus button on the Zotero toolbar.