Gotta love Diigo.  I selected this tool Because I saw it in "Information R/evolution" by Michael Wesch on YouTube and I wanted to explore the application. 

Diigo www.diigo.com  is a Bookmarking service that permits you to highlight and annotate your bookmarks with sticky notes.  It appears to be geared toward research and building research community.  Check out the Diigo video:

Diigo boasts that its Free educators account is designed specifically for that use, something I haven't seen on other bookmarking websites.  Since everything I need to know I can learn on YouTube I challenged this assumption by searching "Diigo and Educator" and I found this explanation of how one teacher is using a Diigo group with students and as a tool for providing feedback.

Another feature of Diigo is called "WebSlides" - a webslideshow that has its own url and can be posted to many other Web 2.0 applications, like a blog.  You can create a guided tour to a website with this service, which might be helpful for instructing students on how to use other Web 2.0 tool, and also content based web research for any discipline.  Once again, a quick YouTube preview

Enjoy Diigo