The link below is to an article, which though old, will still be a useful introduction to the bookmarking service Diigo. The service is so much more than a bookmarking service though, being a very useful service for research and online library building.

Diigo V5: Collect and Highlight, Then Remember! from diigobuzz on Vimeo.

For more visit:
http://www.knowthenetwork.com/2010/01/turning-links-into-a-library-with-diigo/