I tried out Diigo educator and was REALLY impressed. This let me very quickly (and with no email addresses needed) set up accounts for 30 students. I then created a group for all 3 classes to use and added all the students to the group. In this case, since I only have one more day with the kids and am not sure if they'll be using Diigo after this, I just used the 30 accounts for multiple classes, but if this were for my actual students, I would have created an account for each student. Anyway, once all the students were added to the group, I just instructed them to make sure to share every bookmark for this project with the group. All of the students will then be able to view all of the bookmarks. Again, we couldn't install even the diigolet, but saving right from Diigo worked fine for our purposes. They used the same technique of tagging with last name, class hour, and other appropriate tags.
I taught both of these methods in a 45 minute class period and the actual explanation of the bookmarking technique took only 7-10 min. of each class period. The kids (7th graders) picked up on it EXTREMELY fast.