Diigo is an awesome tool to use in the classroom. Teachers across the globe have used the social bookmarking tool to motivate and engage students in collaborative learning
If you find a key paragraph about the topic your students are researching, you can highlight it and then bookmark the page. As long as you're logged into Diigo, every time you visit that page, the paragraph will be highlighted
Highlight text and pictures in a variety of colors and add sticky notes to a bookmarked page
Categorize websites with titles, notes, keyword tags, lists, and groups