On the University of Illinois GSLIS Tech Tutorials site, social cataloging is defined as "Social cataloging applications allow users to catalog their collections while interacting on a social networking level." These apps allow readers to track, review, and rate the books they read. Additionally, they can choose to share their feedback with friends or the public in general.
Goodreads is one of several social cataloging sites which also offers widgets to embed on your library sites. Those widgets include a shelf, updates, grid, shelf badge, quotation, email footer, and reading challenge. I have created a guide with a sample of each of these widgets. Because of these additional features, I tend to favor this app.
Anobii's online presence is similar to that of Goodreads and Shelfari. Books may be organized on a shelf. The shelf may then be shared with others via a link. Options to share with RSS feed or via Twitter or Facebook are provided. The app allows viewing and updating of your shelf. Books can be added to the shelf through searching or scanning the bar code. Syncing does occur between the app and the web site, but be patient. The free app is available for iOS and Android devices.
Bookish came to my attention because some of our members use it. Bookish allows readers to add books to their shelves in a variety of ways including uploading a csv. file of the contents of your Goodreads shelves. The free Bookish app is a ereader for books you have purchased from them or import from other web sites. It does not appear to let you share your online shelves with non members. It is available for iOS and Android devices ( app appears to no longer be availble 10/13).
iBookshelf is an open source application that I wanted about which I wnated to make you aware. However, I have chosen not to download the application at this point to my desktop. Links are provided for both the free and modestly priced apps and information about this option. I have also included a short video about this application. The full version has received very positive reviews.