Josh: Diigo is a web-based tool for what the company is calling "social annotation." It lets users highlight, annotate (via sticky notes), and clip information from any web site. What I think makes Diigo potentially very useful is that you can share your annotations, clippings and bookmarks with a group. For students and professors I think Diigo could help groups organize their thoughts and research for team projects. Marshall reviewed them a year ago for TechCrunch.