There is a great video describing social bookmarking :Social Bookmarking Video
The description pretty much describes how to use Connotea as well, except of course with Connotea you get extra citation meta-data when you bookmark an academic paper, and you can import and export in many different formats too.
Lee Lefever (him and his wife Sachi are Commoncraft) is amazing, and a nice fellow to boot. Anyone remotely interested in web stuff and video has to check out all the Common Craft videos