Zotero

EasyBib: a basic bibliography/citation maker. Works through an on-line interface to build a reference list, which you can then export to MS Word or another word processing programme in RTF. If you register, you can save multiple reference lists online and share them with other users and such. I didn’t register (even though it’s free), so I can’t vouch for whether or not this works well. Major drawback is that it only builds bibliographies in MLA style. A cool feature is if you’re citing a book and you have the ISBN, EasyBib can automatically populate the reference fields for you.

drag the link from the page onto the reference in your library. Zotero stores and attaches the PDF for you.

Zotero can index your PDF attachments and make them fully searchable, turning your library from a mere linked catalogue into a Google Books of sorts.

Want to tag multiple items at once? Select them, make sure the tag selector is visible in the left pane, and drag them onto the tag you want to use. The tag will be applied to all items.