I received an email the other week asking me to take part in and review a new service which finally launched outright this week called "Diigo".It's nice to know that people read my blog, enjoy what I ramble on about and would like me to comment on it, but anyway, on with the review.Diigo is a not your usual social bookmarking site like del.icio.us or social commentary site like Reddit or Digg, they call it a "Social Annotation website".They have a toolbar that integrates with Firefox, Flock and Internet Explorer that allows you to add "Sticky notes" to pages, post the pages to a del.icio.us-type bookmarking service (and del.icio.us itself plus others), forward highlighted text via email to a friend and, most importantly, add comments to webpages which other users can then view (or you could choose to make them private but that's hardly the point of a social annotation site now is it?!).After you have your Diigo account, you'll be prompted to install the relevant toolbar for your browser (Sorry Safari fans, I don't think you're supported yet), once that's installed and you've restarted your browser the fun begins!The annotation system is accessed via a your context menu (right-click on the webpage):