Annotary provides social bookmarking through a visually appealing interface.
Search through and share useful applications using edshelf, an online repository of links to and reviews of Web 2.0 tools. A bit like this really!
Create online lists where students (or colleagues) can add items AND vote items in the list up or down with List.ly.
Share links and resources in a visual ‘Pinterest’-like way with other educlipper users or even with classes you choose to set up.
An online bookmarking tool, Yummymarks means you can access your bookmarks from any computer with an Internet connection.
LinCut provides you with an online bookmarking service for which registration isn’t needed.
Pumped-up social bookmarking and annotations from Diigo, together with features aimed specifically at educators and learners.
This video succinctly describes what Diigo can do for you.