As Laure has seen from her research - there are dozens of social bookmarking sites - all working slightly differently.

I would say there are some obvious ones, like Digg, and the Asian countries use social bookmarking in an integrated way.

Please gather info here!

About has listed its top 10
http://websearch.about.com/od/bestwe...ebookmarks.htm

And this site is quite good
http://www.blogmarketingtactics.com/...top-links.html