“Cluztr is another way to socialize your browsing behavior online.Cluztr is different from social bookmarking services like del.icio.us or digg because you don’t have to actively tag the sites you like.”
http://www.curioustalk.com/1333/cluztr-making-browsing-social/
That’s my site, but the article is actually from Mashable…
http://mashable.com/2007/04/12/clutzr/