I have been doing some research lately on online bookmarking web sites. There are dozens out there and I have tried many, however none have really done everything I wanted. Recently I have been exploring Diigo and Google Notebook. Both do bookmarking, but also provide ways to annotate and highlight information on the web page. I'm not going to do a full review of these, you can find those at Solution Watch Review for Diigo and Google Notebook, but I do want to say I'm excited about the collaborative possibilities of each.  
 
I also really like that you can add notes or annotate your ideas directly on a web page. For me, this is a great feature. Often times I'm doing research on a topic and bookmark many pages in the process. My problem is when I go back to review them, I often can't recall exactly what I was interested in initially. Being able to highlight a part or add some notes to myself has been extremely useful for me. It does take some extra time and effort, but I've found it makes my research more valuable. I'm a new user to both of these sites, so I have a lot to learn, however I'm excited by the new possibility of these services for teaching and learning.  
 
If you are using them, let me know what you think. You can view my evolving Google Notebook on Digital Storytelling.