I would recommend using "Diigo" for social bookmarking activities in your class. The reason for this is that diigo allows pupils to bookmark websites and add them to the class repository but also has the added feature of allowing pupils to annotate the webpages that they bookmark. Diigo allows its users to highlight text and add "stick notes" to webpages which allows pupils to highlight the useful information and add notes of applicable information they may know. Diigo also offers features that help it to integrate effectively with blogging software which means it can be used almost seamlessly with the classroom blog and the pupils' individual blogs.
Creating an Educator Account
Creating Student Accounts
Managing Groups Tutorial
Installing and Using the Diigo Toolbar Tutorial
For all there is to know about using Diigo here is a link to their comprehensive user guide
This website has been created by Paul Leacy (0744034) in 2011 as part of his Final Year Project in the University of Limerick as part of the (B.Tech. Ed.) course in Materials and Construction Technology.