If you use Diigo but are researching a certain topic for a book or term paper and also use Evernote, I recommend setting up an ifttt.com recipe similar to this one I'm using for my collaborative writing book. Everything tagged "collaborative writing" goes automatically to my collaborative writing book.
You could use this for a course. You could take everything on Diigo tagged with the course number into a notebook (or into a Google spreadsheet, for that matter.) There are many other sources of information you can use to collect information on a topic in one place.
In a recent PEW study, National Writing Project (NWP) and Advanced Placement (AP) teachers said that “a top priority in today’s classrooms should be teaching students how to ‘judge the quality of online information.’” Furthermore, teachers are concerned that students don’t get past Google, Wikipedia, and YouTube into deeper (and more accurate) ways of collecting information. If you want to discuss research sources, social bookmarking is the best way to do this. We should see more classrooms using Diigo (the most superior bookmarking service, in my opinion) or Delicious as they discuss and share the documents they will use in their research papers.
I’ve found when topics need deeper research or when the sources of research are in dispute, that social bookmarking is the best way to facilitate those discussions. It is a powerful form of pre-writing for students. If they can begin the conversations around research articles and sources, then more accurate information will emerge in their final document. Often students don’t verify the sources of information and should learn to view all online information with skepticism and a critical eye as they converse over what makes a good source. Social bookmarking is a key source of discussion, data collection, and citation in the modern classroom.