"If you browse or read a lot on the web, we believe you will find Diigo indispensable. Diigo is two services in one -- it is a research and collaborative research tool on the one hand, and a knowledge-sharing community and social content site on the other." http://www.diigo.com/about Not only can you bookmark sites, but you can share them to specific people, groups, lists, and everyone in the world. You can highlight the pages and add sticky notes for yourself, your group or the public. You can easily capture and annotate images on the web to save to your virtual library. And that's not all... check out the about page and the video below to learn more about Diigo: