Includes a comparison chart (Diigo, Delicious, Browser) and a high level overview of Diigo (including screenshots). According to Ruffini, Diigo "fosters research-sharing and collaboration in new ways. Not only can students bookmark, organize, and collaborate on various projects and research, but this service gives them - and teachers - the opportunity to organize and manage web resources and documents. Diigo has useful educational applications, as well, such as organizing bookmarks for resources and research, collaborative learning, and professional development."
Taking the Mystery out of Copyright is a site from the US Library of Congress that uses animations to teach about copyrights and copyright laws. It's fun and educational and easy to understand.
The Library of Congress also has a lot of other great resources for educators.