Here are my two links to my Diigo websites/articles: http://diigo.com/0ec5l and http://diigo.com/0ec5s.
Like Alicia, I have mixed feelings about this tool. I feel that it is useful for people who already understand the research process and simply need an internet tool to take notes or highlight key information. Personally, though, I still prefer to print out my articles and highlight on the actual paper. Reading on the computer is difficult for me, and it is much harder for me to concentrate. Also, I found the annotating process to be quite cumbersome. I felt like I could write my notes by hand faster than I could click and type.
One feature I really liked was the ability to send highlights and annotations to others. As a teacher, I think this would make the grading process much easier during major research projects. It would save paper and time (students would not have to transfer their work on the internet to a piece that could be physically turned in). I also think that using a site like this might make the research process more interesting for students ... at least until the novelty of Diigo wore off.
I don't think Diigo is the way to go for students just learning the research process. However, I do believe that the tool might be useful for our seniors. In most college English classes today, few professors require students to turn in all of their research and the steps they took to create the actual research paper (working bib cards, note cards, etc.). Instead, professors just want to see the final product. Teaching our seniors this tool could help them learn how to do research for a college-level course and help them internalize the research process. By this, I mean seniors could start to realize that writing a research paper can be done in multiple ways. For example, most of us teachers have written so many papers by this point that we are able to just look up information on our topic, read the research, and then write the paper.
I might possibly use this tool with my Debate classes when they have mini-debates. The purpose of these debates is to provide students with a brief amount of time (usually less than 25 minutes) to read assigned articles about a certain topic and then present a case about that topic. I could see myself taking students into the lab, allowing them to read and highlight for half the period, and then taking them back into the classroom to begin the debates.
All in all, a very intriguing tool. I'm interested to see what others have to say about it.