Social bookmarking sites facilitate word-of-mouth recommendations among colleagues by allowing users to save references and bookmarks to an online account, which may be shared with others. These bookmarks are organized using informal tags created by the user, which in turn can be searched and browsed, much like subject headings. Popular social bookmarking sites include Digg and Reddit.
There are a several academic bookmarking sites, many of which share some of the features of citation managers like Zotero, Mendeley, or Endnote. What sets these sites apart is that they allow you to find out what others are reading and citing, and share your citations with others. Some of the most popular sites are Bibsonomy and CiteULike.
Each Social Bookmarking site varies, and each will have more advanced options once you create an account. But here are some of the basic features.
The image below shows a simple searching for the topic "3D imaging." Note some of the features:
If you were to click on the first article result, "Techniques for Generalizing Building of Geometry of Complex Virtual 3D City Models..." you will see the image below. Notice a few features: