Diggo Extension - Quick capture
Tagging and outliner to group related links
Annotating & Highligthing text
Google search related results.Cons:
Note taking should be worked on so it more usefull.
A little thing that I love is that the extension shows that you already captured the page. Something Evernote Clipper doesn't do.
The Diigo related results on the google search page it a killer feature.Otto Vanluchene has used this product for one year.