For good reasons, Diigo has become one of the most popular social bookmarking services used by educators. Diigo offers good tools for highlighting, annotating, bookmarking, and sharing the gems that you find on the Internet. Yesterday, Jose Picardo (I highly recommend his blog) posted a quick guide to annotating using Diigo. He created the video for his students and if you're considering using Diigo with your students it could be very useful for you too. The video is embedded below.