My latest thing = diigo. I think it's more useful for a teacher than for a student. I may recommend students use it if they have to research something from multiple sites, but I don't know that it is worth the trouble it would be to have them download the tool bar and teach them. I suppose it would cut down on wasted printing, where students print out loads of information to then highlight three things. If they could just annotate it on the computer and save that, maybe they wouldn't print it. I like it to remind myself why I though the article or site was cool. It's cool that you can share it too. I may use it to share a book list or review with my book club, or to send an article to a friend or colleague. I'm hesitant to try it with students though. Maybe I would put links of my annotations up for students to see?
Here is a link to one of the pages I annotated: