I absolutely adore Goodreads. I introduced the site to a patron who is also a published author. He's a young guy trying to get out and noticed in the publishing world. I showed him the way to join Goodreads as an author. He's so excited about the potential exposure.
I realize that I can always learn more so I'm also registered for the Technology with Tine: Goodreads and Shelfari webinar next week (02/10/12).
I checked out Zotero. I haven't had an opportunity to show any of our student patrons the site. We have several adult patrons taking online classes with Angelina College and Lamar University.