...Diigo, and ZigTag by boasting a better interface, more users, and better tagging, which makes it easier to find and sharebookmarks. Although Diigo's highlighting options are useful, ZigTag's semantic technology tries to improve bookmarking...
http://news.cnet.com/8301-17939_109-10131710-2.html
...nine popular Web site where you'd save links and sharebookmarks, including del.icio.us, Digg, Facebook...service, there's no faster way than Shareaholic to sharebookmarks, and gauge the popularity of a page across different...
http://www.linux.com/feature/154811